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+from __future__ import annotations
+
+import collections.abc
+import tempfile
+import sys
+import warnings
+import operator
+import io
+import itertools
+import functools
+import ctypes
+import os
+import gc
+import re
+import weakref
+import pytest
+from contextlib import contextmanager
+
+from numpy.compat import pickle
+
+import pathlib
+import builtins
+from decimal import Decimal
+import mmap
+
+import numpy as np
+import numpy.core._multiarray_tests as _multiarray_tests
+from numpy.core._rational_tests import rational
+from numpy.testing import (
+    assert_, assert_raises, assert_warns, assert_equal, assert_almost_equal,
+    assert_array_equal, assert_raises_regex, assert_array_almost_equal,
+    assert_allclose, IS_PYPY, IS_PYSTON, HAS_REFCOUNT, assert_array_less,
+    runstring, temppath, suppress_warnings, break_cycles, _SUPPORTS_SVE,
+    )
+from numpy.testing._private.utils import requires_memory, _no_tracing
+from numpy.core.tests._locales import CommaDecimalPointLocale
+from numpy.lib.recfunctions import repack_fields
+from numpy.core.multiarray import _get_ndarray_c_version
+
+# Need to test an object that does not fully implement math interface
+from datetime import timedelta, datetime
+
+
+def assert_arg_sorted(arr, arg):
+    # resulting array should be sorted and arg values should be unique
+    assert_equal(arr[arg], np.sort(arr))
+    assert_equal(np.sort(arg), np.arange(len(arg)))
+
+
+def _aligned_zeros(shape, dtype=float, order="C", align=None):
+    """
+    Allocate a new ndarray with aligned memory.
+
+    The ndarray is guaranteed *not* aligned to twice the requested alignment.
+    Eg, if align=4, guarantees it is not aligned to 8. If align=None uses
+    dtype.alignment."""
+    dtype = np.dtype(dtype)
+    if dtype == np.dtype(object):
+        # Can't do this, fall back to standard allocation (which
+        # should always be sufficiently aligned)
+        if align is not None:
+            raise ValueError("object array alignment not supported")
+        return np.zeros(shape, dtype=dtype, order=order)
+    if align is None:
+        align = dtype.alignment
+    if not hasattr(shape, '__len__'):
+        shape = (shape,)
+    size = functools.reduce(operator.mul, shape) * dtype.itemsize
+    buf = np.empty(size + 2*align + 1, np.uint8)
+
+    ptr = buf.__array_interface__['data'][0]
+    offset = ptr % align
+    if offset != 0:
+        offset = align - offset
+    if (ptr % (2*align)) == 0:
+        offset += align
+
+    # Note: slices producing 0-size arrays do not necessarily change
+    # data pointer --- so we use and allocate size+1
+    buf = buf[offset:offset+size+1][:-1]
+    buf.fill(0)
+    data = np.ndarray(shape, dtype, buf, order=order)
+    return data
+
+
+class TestFlags:
+    def setup_method(self):
+        self.a = np.arange(10)
+
+    def test_writeable(self):
+        mydict = locals()
+        self.a.flags.writeable = False
+        assert_raises(ValueError, runstring, 'self.a[0] = 3', mydict)
+        assert_raises(ValueError, runstring, 'self.a[0:1].itemset(3)', mydict)
+        self.a.flags.writeable = True
+        self.a[0] = 5
+        self.a[0] = 0
+
+    def test_writeable_any_base(self):
+        # Ensure that any base being writeable is sufficient to change flag;
+        # this is especially interesting for arrays from an array interface.
+        arr = np.arange(10)
+
+        class subclass(np.ndarray):
+            pass
+
+        # Create subclass so base will not be collapsed, this is OK to change
+        view1 = arr.view(subclass)
+        view2 = view1[...]
+        arr.flags.writeable = False
+        view2.flags.writeable = False
+        view2.flags.writeable = True  # Can be set to True again.
+
+        arr = np.arange(10)
+
+        class frominterface:
+            def __init__(self, arr):
+                self.arr = arr
+                self.__array_interface__ = arr.__array_interface__
+
+        view1 = np.asarray(frominterface)
+        view2 = view1[...]
+        view2.flags.writeable = False
+        view2.flags.writeable = True
+
+        view1.flags.writeable = False
+        view2.flags.writeable = False
+        with assert_raises(ValueError):
+            # Must assume not writeable, since only base is not:
+            view2.flags.writeable = True
+
+    def test_writeable_from_readonly(self):
+        # gh-9440 - make sure fromstring, from buffer on readonly buffers
+        # set writeable False
+        data = b'\x00' * 100
+        vals = np.frombuffer(data, 'B')
+        assert_raises(ValueError, vals.setflags, write=True)
+        types = np.dtype( [('vals', 'u1'), ('res3', 'S4')] )
+        values = np.core.records.fromstring(data, types)
+        vals = values['vals']
+        assert_raises(ValueError, vals.setflags, write=True)
+
+    def test_writeable_from_buffer(self):
+        data = bytearray(b'\x00' * 100)
+        vals = np.frombuffer(data, 'B')
+        assert_(vals.flags.writeable)
+        vals.setflags(write=False)
+        assert_(vals.flags.writeable is False)
+        vals.setflags(write=True)
+        assert_(vals.flags.writeable)
+        types = np.dtype( [('vals', 'u1'), ('res3', 'S4')] )
+        values = np.core.records.fromstring(data, types)
+        vals = values['vals']
+        assert_(vals.flags.writeable)
+        vals.setflags(write=False)
+        assert_(vals.flags.writeable is False)
+        vals.setflags(write=True)
+        assert_(vals.flags.writeable)
+
+    @pytest.mark.skipif(IS_PYPY, reason="PyPy always copies")
+    def test_writeable_pickle(self):
+        import pickle
+        # Small arrays will be copied without setting base.
+        # See condition for using PyArray_SetBaseObject in
+        # array_setstate.
+        a = np.arange(1000)
+        for v in range(pickle.HIGHEST_PROTOCOL):
+            vals = pickle.loads(pickle.dumps(a, v))
+            assert_(vals.flags.writeable)
+            assert_(isinstance(vals.base, bytes))
+
+    def test_writeable_from_c_data(self):
+        # Test that the writeable flag can be changed for an array wrapping
+        # low level C-data, but not owning its data.
+        # Also see that this is deprecated to change from python.
+        from numpy.core._multiarray_tests import get_c_wrapping_array
+
+        arr_writeable = get_c_wrapping_array(True)
+        assert not arr_writeable.flags.owndata
+        assert arr_writeable.flags.writeable
+        view = arr_writeable[...]
+
+        # Toggling the writeable flag works on the view:
+        view.flags.writeable = False
+        assert not view.flags.writeable
+        view.flags.writeable = True
+        assert view.flags.writeable
+        # Flag can be unset on the arr_writeable:
+        arr_writeable.flags.writeable = False
+
+        arr_readonly = get_c_wrapping_array(False)
+        assert not arr_readonly.flags.owndata
+        assert not arr_readonly.flags.writeable
+
+        for arr in [arr_writeable, arr_readonly]:
+            view = arr[...]
+            view.flags.writeable = False  # make sure it is readonly
+            arr.flags.writeable = False
+            assert not arr.flags.writeable
+
+            with assert_raises(ValueError):
+                view.flags.writeable = True
+
+            with warnings.catch_warnings():
+                warnings.simplefilter("error", DeprecationWarning)
+                with assert_raises(DeprecationWarning):
+                    arr.flags.writeable = True
+
+            with assert_warns(DeprecationWarning):
+                arr.flags.writeable = True
+
+    def test_warnonwrite(self):
+        a = np.arange(10)
+        a.flags._warn_on_write = True
+        with warnings.catch_warnings(record=True) as w:
+            warnings.filterwarnings('always')
+            a[1] = 10
+            a[2] = 10
+            # only warn once
+            assert_(len(w) == 1)
+
+    @pytest.mark.parametrize(["flag", "flag_value", "writeable"],
+            [("writeable", True, True),
+             # Delete _warn_on_write after deprecation and simplify
+             # the parameterization:
+             ("_warn_on_write", True, False),
+             ("writeable", False, False)])
+    def test_readonly_flag_protocols(self, flag, flag_value, writeable):
+        a = np.arange(10)
+        setattr(a.flags, flag, flag_value)
+
+        class MyArr():
+            __array_struct__ = a.__array_struct__
+
+        assert memoryview(a).readonly is not writeable
+        assert a.__array_interface__['data'][1] is not writeable
+        assert np.asarray(MyArr()).flags.writeable is writeable
+
+    def test_otherflags(self):
+        assert_equal(self.a.flags.carray, True)
+        assert_equal(self.a.flags['C'], True)
+        assert_equal(self.a.flags.farray, False)
+        assert_equal(self.a.flags.behaved, True)
+        assert_equal(self.a.flags.fnc, False)
+        assert_equal(self.a.flags.forc, True)
+        assert_equal(self.a.flags.owndata, True)
+        assert_equal(self.a.flags.writeable, True)
+        assert_equal(self.a.flags.aligned, True)
+        assert_equal(self.a.flags.writebackifcopy, False)
+        assert_equal(self.a.flags['X'], False)
+        assert_equal(self.a.flags['WRITEBACKIFCOPY'], False)
+
+    def test_string_align(self):
+        a = np.zeros(4, dtype=np.dtype('|S4'))
+        assert_(a.flags.aligned)
+        # not power of two are accessed byte-wise and thus considered aligned
+        a = np.zeros(5, dtype=np.dtype('|S4'))
+        assert_(a.flags.aligned)
+
+    def test_void_align(self):
+        a = np.zeros(4, dtype=np.dtype([("a", "i4"), ("b", "i4")]))
+        assert_(a.flags.aligned)
+
+
+class TestHash:
+    # see #3793
+    def test_int(self):
+        for st, ut, s in [(np.int8, np.uint8, 8),
+                          (np.int16, np.uint16, 16),
+                          (np.int32, np.uint32, 32),
+                          (np.int64, np.uint64, 64)]:
+            for i in range(1, s):
+                assert_equal(hash(st(-2**i)), hash(-2**i),
+                             err_msg="%r: -2**%d" % (st, i))
+                assert_equal(hash(st(2**(i - 1))), hash(2**(i - 1)),
+                             err_msg="%r: 2**%d" % (st, i - 1))
+                assert_equal(hash(st(2**i - 1)), hash(2**i - 1),
+                             err_msg="%r: 2**%d - 1" % (st, i))
+
+                i = max(i - 1, 1)
+                assert_equal(hash(ut(2**(i - 1))), hash(2**(i - 1)),
+                             err_msg="%r: 2**%d" % (ut, i - 1))
+                assert_equal(hash(ut(2**i - 1)), hash(2**i - 1),
+                             err_msg="%r: 2**%d - 1" % (ut, i))
+
+
+class TestAttributes:
+    def setup_method(self):
+        self.one = np.arange(10)
+        self.two = np.arange(20).reshape(4, 5)
+        self.three = np.arange(60, dtype=np.float64).reshape(2, 5, 6)
+
+    def test_attributes(self):
+        assert_equal(self.one.shape, (10,))
+        assert_equal(self.two.shape, (4, 5))
+        assert_equal(self.three.shape, (2, 5, 6))
+        self.three.shape = (10, 3, 2)
+        assert_equal(self.three.shape, (10, 3, 2))
+        self.three.shape = (2, 5, 6)
+        assert_equal(self.one.strides, (self.one.itemsize,))
+        num = self.two.itemsize
+        assert_equal(self.two.strides, (5*num, num))
+        num = self.three.itemsize
+        assert_equal(self.three.strides, (30*num, 6*num, num))
+        assert_equal(self.one.ndim, 1)
+        assert_equal(self.two.ndim, 2)
+        assert_equal(self.three.ndim, 3)
+        num = self.two.itemsize
+        assert_equal(self.two.size, 20)
+        assert_equal(self.two.nbytes, 20*num)
+        assert_equal(self.two.itemsize, self.two.dtype.itemsize)
+        assert_equal(self.two.base, np.arange(20))
+
+    def test_dtypeattr(self):
+        assert_equal(self.one.dtype, np.dtype(np.int_))
+        assert_equal(self.three.dtype, np.dtype(np.float_))
+        assert_equal(self.one.dtype.char, 'l')
+        assert_equal(self.three.dtype.char, 'd')
+        assert_(self.three.dtype.str[0] in '<>')
+        assert_equal(self.one.dtype.str[1], 'i')
+        assert_equal(self.three.dtype.str[1], 'f')
+
+    def test_int_subclassing(self):
+        # Regression test for https://github.com/numpy/numpy/pull/3526
+
+        numpy_int = np.int_(0)
+
+        # int_ doesn't inherit from Python int, because it's not fixed-width
+        assert_(not isinstance(numpy_int, int))
+
+    def test_stridesattr(self):
+        x = self.one
+
+        def make_array(size, offset, strides):
+            return np.ndarray(size, buffer=x, dtype=int,
+                              offset=offset*x.itemsize,
+                              strides=strides*x.itemsize)
+
+        assert_equal(make_array(4, 4, -1), np.array([4, 3, 2, 1]))
+        assert_raises(ValueError, make_array, 4, 4, -2)
+        assert_raises(ValueError, make_array, 4, 2, -1)
+        assert_raises(ValueError, make_array, 8, 3, 1)
+        assert_equal(make_array(8, 3, 0), np.array([3]*8))
+        # Check behavior reported in gh-2503:
+        assert_raises(ValueError, make_array, (2, 3), 5, np.array([-2, -3]))
+        make_array(0, 0, 10)
+
+    def test_set_stridesattr(self):
+        x = self.one
+
+        def make_array(size, offset, strides):
+            try:
+                r = np.ndarray([size], dtype=int, buffer=x,
+                               offset=offset*x.itemsize)
+            except Exception as e:
+                raise RuntimeError(e)
+            r.strides = strides = strides*x.itemsize
+            return r
+
+        assert_equal(make_array(4, 4, -1), np.array([4, 3, 2, 1]))
+        assert_equal(make_array(7, 3, 1), np.array([3, 4, 5, 6, 7, 8, 9]))
+        assert_raises(ValueError, make_array, 4, 4, -2)
+        assert_raises(ValueError, make_array, 4, 2, -1)
+        assert_raises(RuntimeError, make_array, 8, 3, 1)
+        # Check that the true extent of the array is used.
+        # Test relies on as_strided base not exposing a buffer.
+        x = np.lib.stride_tricks.as_strided(np.arange(1), (10, 10), (0, 0))
+
+        def set_strides(arr, strides):
+            arr.strides = strides
+
+        assert_raises(ValueError, set_strides, x, (10*x.itemsize, x.itemsize))
+
+        # Test for offset calculations:
+        x = np.lib.stride_tricks.as_strided(np.arange(10, dtype=np.int8)[-1],
+                                                    shape=(10,), strides=(-1,))
+        assert_raises(ValueError, set_strides, x[::-1], -1)
+        a = x[::-1]
+        a.strides = 1
+        a[::2].strides = 2
+
+        # test 0d
+        arr_0d = np.array(0)
+        arr_0d.strides = ()
+        assert_raises(TypeError, set_strides, arr_0d, None)
+
+    def test_fill(self):
+        for t in "?bhilqpBHILQPfdgFDGO":
+            x = np.empty((3, 2, 1), t)
+            y = np.empty((3, 2, 1), t)
+            x.fill(1)
+            y[...] = 1
+            assert_equal(x, y)
+
+    def test_fill_max_uint64(self):
+        x = np.empty((3, 2, 1), dtype=np.uint64)
+        y = np.empty((3, 2, 1), dtype=np.uint64)
+        value = 2**64 - 1
+        y[...] = value
+        x.fill(value)
+        assert_array_equal(x, y)
+
+    def test_fill_struct_array(self):
+        # Filling from a scalar
+        x = np.array([(0, 0.0), (1, 1.0)], dtype='i4,f8')
+        x.fill(x[0])
+        assert_equal(x['f1'][1], x['f1'][0])
+        # Filling from a tuple that can be converted
+        # to a scalar
+        x = np.zeros(2, dtype=[('a', 'f8'), ('b', 'i4')])
+        x.fill((3.5, -2))
+        assert_array_equal(x['a'], [3.5, 3.5])
+        assert_array_equal(x['b'], [-2, -2])
+
+    def test_fill_readonly(self):
+        # gh-22922
+        a = np.zeros(11)
+        a.setflags(write=False)
+        with pytest.raises(ValueError, match=".*read-only"):
+            a.fill(0)
+
+
+class TestArrayConstruction:
+    def test_array(self):
+        d = np.ones(6)
+        r = np.array([d, d])
+        assert_equal(r, np.ones((2, 6)))
+
+        d = np.ones(6)
+        tgt = np.ones((2, 6))
+        r = np.array([d, d])
+        assert_equal(r, tgt)
+        tgt[1] = 2
+        r = np.array([d, d + 1])
+        assert_equal(r, tgt)
+
+        d = np.ones(6)
+        r = np.array([[d, d]])
+        assert_equal(r, np.ones((1, 2, 6)))
+
+        d = np.ones(6)
+        r = np.array([[d, d], [d, d]])
+        assert_equal(r, np.ones((2, 2, 6)))
+
+        d = np.ones((6, 6))
+        r = np.array([d, d])
+        assert_equal(r, np.ones((2, 6, 6)))
+
+        d = np.ones((6, ))
+        r = np.array([[d, d + 1], d + 2], dtype=object)
+        assert_equal(len(r), 2)
+        assert_equal(r[0], [d, d + 1])
+        assert_equal(r[1], d + 2)
+
+        tgt = np.ones((2, 3), dtype=bool)
+        tgt[0, 2] = False
+        tgt[1, 0:2] = False
+        r = np.array([[True, True, False], [False, False, True]])
+        assert_equal(r, tgt)
+        r = np.array([[True, False], [True, False], [False, True]])
+        assert_equal(r, tgt.T)
+
+    def test_array_empty(self):
+        assert_raises(TypeError, np.array)
+
+    def test_0d_array_shape(self):
+        assert np.ones(np.array(3)).shape == (3,)
+
+    def test_array_copy_false(self):
+        d = np.array([1, 2, 3])
+        e = np.array(d, copy=False)
+        d[1] = 3
+        assert_array_equal(e, [1, 3, 3])
+        e = np.array(d, copy=False, order='F')
+        d[1] = 4
+        assert_array_equal(e, [1, 4, 3])
+        e[2] = 7
+        assert_array_equal(d, [1, 4, 7])
+
+    def test_array_copy_true(self):
+        d = np.array([[1,2,3], [1, 2, 3]])
+        e = np.array(d, copy=True)
+        d[0, 1] = 3
+        e[0, 2] = -7
+        assert_array_equal(e, [[1, 2, -7], [1, 2, 3]])
+        assert_array_equal(d, [[1, 3, 3], [1, 2, 3]])
+        e = np.array(d, copy=True, order='F')
+        d[0, 1] = 5
+        e[0, 2] = 7
+        assert_array_equal(e, [[1, 3, 7], [1, 2, 3]])
+        assert_array_equal(d, [[1, 5, 3], [1,2,3]])
+
+    def test_array_cont(self):
+        d = np.ones(10)[::2]
+        assert_(np.ascontiguousarray(d).flags.c_contiguous)
+        assert_(np.ascontiguousarray(d).flags.f_contiguous)
+        assert_(np.asfortranarray(d).flags.c_contiguous)
+        assert_(np.asfortranarray(d).flags.f_contiguous)
+        d = np.ones((10, 10))[::2,::2]
+        assert_(np.ascontiguousarray(d).flags.c_contiguous)
+        assert_(np.asfortranarray(d).flags.f_contiguous)
+
+    @pytest.mark.parametrize("func",
+            [np.array,
+             np.asarray,
+             np.asanyarray,
+             np.ascontiguousarray,
+             np.asfortranarray])
+    def test_bad_arguments_error(self, func):
+        with pytest.raises(TypeError):
+            func(3, dtype="bad dtype")
+        with pytest.raises(TypeError):
+            func()  # missing arguments
+        with pytest.raises(TypeError):
+            func(1, 2, 3, 4, 5, 6, 7, 8)  # too many arguments
+
+    @pytest.mark.parametrize("func",
+            [np.array,
+             np.asarray,
+             np.asanyarray,
+             np.ascontiguousarray,
+             np.asfortranarray])
+    def test_array_as_keyword(self, func):
+        # This should likely be made positional only, but do not change
+        # the name accidentally.
+        if func is np.array:
+            func(object=3)
+        else:
+            func(a=3)
+
+
+class TestAssignment:
+    def test_assignment_broadcasting(self):
+        a = np.arange(6).reshape(2, 3)
+
+        # Broadcasting the input to the output
+        a[...] = np.arange(3)
+        assert_equal(a, [[0, 1, 2], [0, 1, 2]])
+        a[...] = np.arange(2).reshape(2, 1)
+        assert_equal(a, [[0, 0, 0], [1, 1, 1]])
+
+        # For compatibility with <= 1.5, a limited version of broadcasting
+        # the output to the input.
+        #
+        # This behavior is inconsistent with NumPy broadcasting
+        # in general, because it only uses one of the two broadcasting
+        # rules (adding a new "1" dimension to the left of the shape),
+        # applied to the output instead of an input. In NumPy 2.0, this kind
+        # of broadcasting assignment will likely be disallowed.
+        a[...] = np.arange(6)[::-1].reshape(1, 2, 3)
+        assert_equal(a, [[5, 4, 3], [2, 1, 0]])
+        # The other type of broadcasting would require a reduction operation.
+
+        def assign(a, b):
+            a[...] = b
+
+        assert_raises(ValueError, assign, a, np.arange(12).reshape(2, 2, 3))
+
+    def test_assignment_errors(self):
+        # Address issue #2276
+        class C:
+            pass
+        a = np.zeros(1)
+
+        def assign(v):
+            a[0] = v
+
+        assert_raises((AttributeError, TypeError), assign, C())
+        assert_raises(ValueError, assign, [1])
+
+    def test_unicode_assignment(self):
+        # gh-5049
+        from numpy.core.numeric import set_string_function
+
+        @contextmanager
+        def inject_str(s):
+            """ replace ndarray.__str__ temporarily """
+            set_string_function(lambda x: s, repr=False)
+            try:
+                yield
+            finally:
+                set_string_function(None, repr=False)
+
+        a1d = np.array(['test'])
+        a0d = np.array('done')
+        with inject_str('bad'):
+            a1d[0] = a0d  # previously this would invoke __str__
+        assert_equal(a1d[0], 'done')
+
+        # this would crash for the same reason
+        np.array([np.array('\xe5\xe4\xf6')])
+
+    def test_stringlike_empty_list(self):
+        # gh-8902
+        u = np.array(['done'])
+        b = np.array([b'done'])
+
+        class bad_sequence:
+            def __getitem__(self): pass
+            def __len__(self): raise RuntimeError
+
+        assert_raises(ValueError, operator.setitem, u, 0, [])
+        assert_raises(ValueError, operator.setitem, b, 0, [])
+
+        assert_raises(ValueError, operator.setitem, u, 0, bad_sequence())
+        assert_raises(ValueError, operator.setitem, b, 0, bad_sequence())
+
+    def test_longdouble_assignment(self):
+        # only relevant if longdouble is larger than float
+        # we're looking for loss of precision
+
+        for dtype in (np.longdouble, np.longcomplex):
+            # gh-8902
+            tinyb = np.nextafter(np.longdouble(0), 1).astype(dtype)
+            tinya = np.nextafter(np.longdouble(0), -1).astype(dtype)
+
+            # construction
+            tiny1d = np.array([tinya])
+            assert_equal(tiny1d[0], tinya)
+
+            # scalar = scalar
+            tiny1d[0] = tinyb
+            assert_equal(tiny1d[0], tinyb)
+
+            # 0d = scalar
+            tiny1d[0, ...] = tinya
+            assert_equal(tiny1d[0], tinya)
+
+            # 0d = 0d
+            tiny1d[0, ...] = tinyb[...]
+            assert_equal(tiny1d[0], tinyb)
+
+            # scalar = 0d
+            tiny1d[0] = tinyb[...]
+            assert_equal(tiny1d[0], tinyb)
+
+            arr = np.array([np.array(tinya)])
+            assert_equal(arr[0], tinya)
+
+    def test_cast_to_string(self):
+        # cast to str should do "str(scalar)", not "str(scalar.item())"
+        # Example: In python2, str(float) is truncated, so we want to avoid
+        # str(np.float64(...).item()) as this would incorrectly truncate.
+        a = np.zeros(1, dtype='S20')
+        a[:] = np.array(['1.12345678901234567890'], dtype='f8')
+        assert_equal(a[0], b"1.1234567890123457")
+
+
+class TestDtypedescr:
+    def test_construction(self):
+        d1 = np.dtype('i4')
+        assert_equal(d1, np.dtype(np.int32))
+        d2 = np.dtype('f8')
+        assert_equal(d2, np.dtype(np.float64))
+
+    def test_byteorders(self):
+        assert_(np.dtype('<i4') != np.dtype('>i4'))
+        assert_(np.dtype([('a', '<i4')]) != np.dtype([('a', '>i4')]))
+
+    def test_structured_non_void(self):
+        fields = [('a', '<i2'), ('b', '<i2')]
+        dt_int = np.dtype(('i4', fields))
+        assert_equal(str(dt_int), "(numpy.int32, [('a', '<i2'), ('b', '<i2')])")
+
+        # gh-9821
+        arr_int = np.zeros(4, dt_int)
+        assert_equal(repr(arr_int),
+            "array([0, 0, 0, 0], dtype=(numpy.int32, [('a', '<i2'), ('b', '<i2')]))")
+
+
+class TestZeroRank:
+    def setup_method(self):
+        self.d = np.array(0), np.array('x', object)
+
+    def test_ellipsis_subscript(self):
+        a, b = self.d
+        assert_equal(a[...], 0)
+        assert_equal(b[...], 'x')
+        assert_(a[...].base is a)  # `a[...] is a` in numpy <1.9.
+        assert_(b[...].base is b)  # `b[...] is b` in numpy <1.9.
+
+    def test_empty_subscript(self):
+        a, b = self.d
+        assert_equal(a[()], 0)
+        assert_equal(b[()], 'x')
+        assert_(type(a[()]) is a.dtype.type)
+        assert_(type(b[()]) is str)
+
+    def test_invalid_subscript(self):
+        a, b = self.d
+        assert_raises(IndexError, lambda x: x[0], a)
+        assert_raises(IndexError, lambda x: x[0], b)
+        assert_raises(IndexError, lambda x: x[np.array([], int)], a)
+        assert_raises(IndexError, lambda x: x[np.array([], int)], b)
+
+    def test_ellipsis_subscript_assignment(self):
+        a, b = self.d
+        a[...] = 42
+        assert_equal(a, 42)
+        b[...] = ''
+        assert_equal(b.item(), '')
+
+    def test_empty_subscript_assignment(self):
+        a, b = self.d
+        a[()] = 42
+        assert_equal(a, 42)
+        b[()] = ''
+        assert_equal(b.item(), '')
+
+    def test_invalid_subscript_assignment(self):
+        a, b = self.d
+
+        def assign(x, i, v):
+            x[i] = v
+
+        assert_raises(IndexError, assign, a, 0, 42)
+        assert_raises(IndexError, assign, b, 0, '')
+        assert_raises(ValueError, assign, a, (), '')
+
+    def test_newaxis(self):
+        a, b = self.d
+        assert_equal(a[np.newaxis].shape, (1,))
+        assert_equal(a[..., np.newaxis].shape, (1,))
+        assert_equal(a[np.newaxis, ...].shape, (1,))
+        assert_equal(a[..., np.newaxis].shape, (1,))
+        assert_equal(a[np.newaxis, ..., np.newaxis].shape, (1, 1))
+        assert_equal(a[..., np.newaxis, np.newaxis].shape, (1, 1))
+        assert_equal(a[np.newaxis, np.newaxis, ...].shape, (1, 1))
+        assert_equal(a[(np.newaxis,)*10].shape, (1,)*10)
+
+    def test_invalid_newaxis(self):
+        a, b = self.d
+
+        def subscript(x, i):
+            x[i]
+
+        assert_raises(IndexError, subscript, a, (np.newaxis, 0))
+        assert_raises(IndexError, subscript, a, (np.newaxis,)*50)
+
+    def test_constructor(self):
+        x = np.ndarray(())
+        x[()] = 5
+        assert_equal(x[()], 5)
+        y = np.ndarray((), buffer=x)
+        y[()] = 6
+        assert_equal(x[()], 6)
+
+        # strides and shape must be the same length
+        with pytest.raises(ValueError):
+            np.ndarray((2,), strides=())
+        with pytest.raises(ValueError):
+            np.ndarray((), strides=(2,))
+
+    def test_output(self):
+        x = np.array(2)
+        assert_raises(ValueError, np.add, x, [1], x)
+
+    def test_real_imag(self):
+        # contiguity checks are for gh-11245
+        x = np.array(1j)
+        xr = x.real
+        xi = x.imag
+
+        assert_equal(xr, np.array(0))
+        assert_(type(xr) is np.ndarray)
+        assert_equal(xr.flags.contiguous, True)
+        assert_equal(xr.flags.f_contiguous, True)
+
+        assert_equal(xi, np.array(1))
+        assert_(type(xi) is np.ndarray)
+        assert_equal(xi.flags.contiguous, True)
+        assert_equal(xi.flags.f_contiguous, True)
+
+
+class TestScalarIndexing:
+    def setup_method(self):
+        self.d = np.array([0, 1])[0]
+
+    def test_ellipsis_subscript(self):
+        a = self.d
+        assert_equal(a[...], 0)
+        assert_equal(a[...].shape, ())
+
+    def test_empty_subscript(self):
+        a = self.d
+        assert_equal(a[()], 0)
+        assert_equal(a[()].shape, ())
+
+    def test_invalid_subscript(self):
+        a = self.d
+        assert_raises(IndexError, lambda x: x[0], a)
+        assert_raises(IndexError, lambda x: x[np.array([], int)], a)
+
+    def test_invalid_subscript_assignment(self):
+        a = self.d
+
+        def assign(x, i, v):
+            x[i] = v
+
+        assert_raises(TypeError, assign, a, 0, 42)
+
+    def test_newaxis(self):
+        a = self.d
+        assert_equal(a[np.newaxis].shape, (1,))
+        assert_equal(a[..., np.newaxis].shape, (1,))
+        assert_equal(a[np.newaxis, ...].shape, (1,))
+        assert_equal(a[..., np.newaxis].shape, (1,))
+        assert_equal(a[np.newaxis, ..., np.newaxis].shape, (1, 1))
+        assert_equal(a[..., np.newaxis, np.newaxis].shape, (1, 1))
+        assert_equal(a[np.newaxis, np.newaxis, ...].shape, (1, 1))
+        assert_equal(a[(np.newaxis,)*10].shape, (1,)*10)
+
+    def test_invalid_newaxis(self):
+        a = self.d
+
+        def subscript(x, i):
+            x[i]
+
+        assert_raises(IndexError, subscript, a, (np.newaxis, 0))
+        assert_raises(IndexError, subscript, a, (np.newaxis,)*50)
+
+    def test_overlapping_assignment(self):
+        # With positive strides
+        a = np.arange(4)
+        a[:-1] = a[1:]
+        assert_equal(a, [1, 2, 3, 3])
+
+        a = np.arange(4)
+        a[1:] = a[:-1]
+        assert_equal(a, [0, 0, 1, 2])
+
+        # With positive and negative strides
+        a = np.arange(4)
+        a[:] = a[::-1]
+        assert_equal(a, [3, 2, 1, 0])
+
+        a = np.arange(6).reshape(2, 3)
+        a[::-1,:] = a[:, ::-1]
+        assert_equal(a, [[5, 4, 3], [2, 1, 0]])
+
+        a = np.arange(6).reshape(2, 3)
+        a[::-1, ::-1] = a[:, ::-1]
+        assert_equal(a, [[3, 4, 5], [0, 1, 2]])
+
+        # With just one element overlapping
+        a = np.arange(5)
+        a[:3] = a[2:]
+        assert_equal(a, [2, 3, 4, 3, 4])
+
+        a = np.arange(5)
+        a[2:] = a[:3]
+        assert_equal(a, [0, 1, 0, 1, 2])
+
+        a = np.arange(5)
+        a[2::-1] = a[2:]
+        assert_equal(a, [4, 3, 2, 3, 4])
+
+        a = np.arange(5)
+        a[2:] = a[2::-1]
+        assert_equal(a, [0, 1, 2, 1, 0])
+
+        a = np.arange(5)
+        a[2::-1] = a[:1:-1]
+        assert_equal(a, [2, 3, 4, 3, 4])
+
+        a = np.arange(5)
+        a[:1:-1] = a[2::-1]
+        assert_equal(a, [0, 1, 0, 1, 2])
+
+
+class TestCreation:
+    """
+    Test the np.array constructor
+    """
+    def test_from_attribute(self):
+        class x:
+            def __array__(self, dtype=None):
+                pass
+
+        assert_raises(ValueError, np.array, x())
+
+    def test_from_string(self):
+        types = np.typecodes['AllInteger'] + np.typecodes['Float']
+        nstr = ['123', '123']
+        result = np.array([123, 123], dtype=int)
+        for type in types:
+            msg = 'String conversion for %s' % type
+            assert_equal(np.array(nstr, dtype=type), result, err_msg=msg)
+
+    def test_void(self):
+        arr = np.array([], dtype='V')
+        assert arr.dtype == 'V8'  # current default
+        # Same length scalars (those that go to the same void) work:
+        arr = np.array([b"1234", b"1234"], dtype="V")
+        assert arr.dtype == "V4"
+
+        # Promoting different lengths will fail (pre 1.20 this worked)
+        # by going via S5 and casting to V5.
+        with pytest.raises(TypeError):
+            np.array([b"1234", b"12345"], dtype="V")
+        with pytest.raises(TypeError):
+            np.array([b"12345", b"1234"], dtype="V")
+
+        # Check the same for the casting path:
+        arr = np.array([b"1234", b"1234"], dtype="O").astype("V")
+        assert arr.dtype == "V4"
+        with pytest.raises(TypeError):
+            np.array([b"1234", b"12345"], dtype="O").astype("V")
+
+    @pytest.mark.parametrize("idx",
+            [pytest.param(Ellipsis, id="arr"), pytest.param((), id="scalar")])
+    def test_structured_void_promotion(self, idx):
+        arr = np.array(
+            [np.array(1, dtype="i,i")[idx], np.array(2, dtype='i,i')[idx]],
+            dtype="V")
+        assert_array_equal(arr, np.array([(1, 1), (2, 2)], dtype="i,i"))
+        # The following fails to promote the two dtypes, resulting in an error
+        with pytest.raises(TypeError):
+            np.array(
+                [np.array(1, dtype="i,i")[idx], np.array(2, dtype='i,i,i')[idx]],
+                dtype="V")
+
+
+    def test_too_big_error(self):
+        # 45341 is the smallest integer greater than sqrt(2**31 - 1).
+        # 3037000500 is the smallest integer greater than sqrt(2**63 - 1).
+        # We want to make sure that the square byte array with those dimensions
+        # is too big on 32 or 64 bit systems respectively.
+        if np.iinfo('intp').max == 2**31 - 1:
+            shape = (46341, 46341)
+        elif np.iinfo('intp').max == 2**63 - 1:
+            shape = (3037000500, 3037000500)
+        else:
+            return
+        assert_raises(ValueError, np.empty, shape, dtype=np.int8)
+        assert_raises(ValueError, np.zeros, shape, dtype=np.int8)
+        assert_raises(ValueError, np.ones, shape, dtype=np.int8)
+
+    @pytest.mark.skipif(np.dtype(np.intp).itemsize != 8,
+                        reason="malloc may not fail on 32 bit systems")
+    def test_malloc_fails(self):
+        # This test is guaranteed to fail due to a too large allocation
+        with assert_raises(np.core._exceptions._ArrayMemoryError):
+            np.empty(np.iinfo(np.intp).max, dtype=np.uint8)
+
+    def test_zeros(self):
+        types = np.typecodes['AllInteger'] + np.typecodes['AllFloat']
+        for dt in types:
+            d = np.zeros((13,), dtype=dt)
+            assert_equal(np.count_nonzero(d), 0)
+            # true for ieee floats
+            assert_equal(d.sum(), 0)
+            assert_(not d.any())
+
+            d = np.zeros(2, dtype='(2,4)i4')
+            assert_equal(np.count_nonzero(d), 0)
+            assert_equal(d.sum(), 0)
+            assert_(not d.any())
+
+            d = np.zeros(2, dtype='4i4')
+            assert_equal(np.count_nonzero(d), 0)
+            assert_equal(d.sum(), 0)
+            assert_(not d.any())
+
+            d = np.zeros(2, dtype='(2,4)i4, (2,4)i4')
+            assert_equal(np.count_nonzero(d), 0)
+
+    @pytest.mark.slow
+    def test_zeros_big(self):
+        # test big array as they might be allocated different by the system
+        types = np.typecodes['AllInteger'] + np.typecodes['AllFloat']
+        for dt in types:
+            d = np.zeros((30 * 1024**2,), dtype=dt)
+            assert_(not d.any())
+            # This test can fail on 32-bit systems due to insufficient
+            # contiguous memory. Deallocating the previous array increases the
+            # chance of success.
+            del(d)
+
+    def test_zeros_obj(self):
+        # test initialization from PyLong(0)
+        d = np.zeros((13,), dtype=object)
+        assert_array_equal(d, [0] * 13)
+        assert_equal(np.count_nonzero(d), 0)
+
+    def test_zeros_obj_obj(self):
+        d = np.zeros(10, dtype=[('k', object, 2)])
+        assert_array_equal(d['k'], 0)
+
+    def test_zeros_like_like_zeros(self):
+        # test zeros_like returns the same as zeros
+        for c in np.typecodes['All']:
+            if c == 'V':
+                continue
+            d = np.zeros((3,3), dtype=c)
+            assert_array_equal(np.zeros_like(d), d)
+            assert_equal(np.zeros_like(d).dtype, d.dtype)
+        # explicitly check some special cases
+        d = np.zeros((3,3), dtype='S5')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+        d = np.zeros((3,3), dtype='U5')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+
+        d = np.zeros((3,3), dtype='<i4')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+        d = np.zeros((3,3), dtype='>i4')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+
+        d = np.zeros((3,3), dtype='<M8[s]')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+        d = np.zeros((3,3), dtype='>M8[s]')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+
+        d = np.zeros((3,3), dtype='f4,f4')
+        assert_array_equal(np.zeros_like(d), d)
+        assert_equal(np.zeros_like(d).dtype, d.dtype)
+
+    def test_empty_unicode(self):
+        # don't throw decode errors on garbage memory
+        for i in range(5, 100, 5):
+            d = np.empty(i, dtype='U')
+            str(d)
+
+    def test_sequence_non_homogeneous(self):
+        assert_equal(np.array([4, 2**80]).dtype, object)
+        assert_equal(np.array([4, 2**80, 4]).dtype, object)
+        assert_equal(np.array([2**80, 4]).dtype, object)
+        assert_equal(np.array([2**80] * 3).dtype, object)
+        assert_equal(np.array([[1, 1],[1j, 1j]]).dtype, complex)
+        assert_equal(np.array([[1j, 1j],[1, 1]]).dtype, complex)
+        assert_equal(np.array([[1, 1, 1],[1, 1j, 1.], [1, 1, 1]]).dtype, complex)
+
+    def test_non_sequence_sequence(self):
+        """Should not segfault.
+
+        Class Fail breaks the sequence protocol for new style classes, i.e.,
+        those derived from object. Class Map is a mapping type indicated by
+        raising a ValueError. At some point we may raise a warning instead
+        of an error in the Fail case.
+
+        """
+        class Fail:
+            def __len__(self):
+                return 1
+
+            def __getitem__(self, index):
+                raise ValueError()
+
+        class Map:
+            def __len__(self):
+                return 1
+
+            def __getitem__(self, index):
+                raise KeyError()
+
+        a = np.array([Map()])
+        assert_(a.shape == (1,))
+        assert_(a.dtype == np.dtype(object))
+        assert_raises(ValueError, np.array, [Fail()])
+
+    def test_no_len_object_type(self):
+        # gh-5100, want object array from iterable object without len()
+        class Point2:
+            def __init__(self):
+                pass
+
+            def __getitem__(self, ind):
+                if ind in [0, 1]:
+                    return ind
+                else:
+                    raise IndexError()
+        d = np.array([Point2(), Point2(), Point2()])
+        assert_equal(d.dtype, np.dtype(object))
+
+    def test_false_len_sequence(self):
+        # gh-7264, segfault for this example
+        class C:
+            def __getitem__(self, i):
+                raise IndexError
+            def __len__(self):
+                return 42
+
+        a = np.array(C()) # segfault?
+        assert_equal(len(a), 0)
+
+    def test_false_len_iterable(self):
+        # Special case where a bad __getitem__ makes us fall back on __iter__:
+        class C:
+            def __getitem__(self, x):
+                raise Exception
+            def __iter__(self):
+                return iter(())
+            def __len__(self):
+                return 2
+
+        a = np.empty(2)
+        with assert_raises(ValueError):
+            a[:] = C()  # Segfault!
+
+        np.array(C()) == list(C())
+
+    def test_failed_len_sequence(self):
+        # gh-7393
+        class A:
+            def __init__(self, data):
+                self._data = data
+            def __getitem__(self, item):
+                return type(self)(self._data[item])
+            def __len__(self):
+                return len(self._data)
+
+        # len(d) should give 3, but len(d[0]) will fail
+        d = A([1,2,3])
+        assert_equal(len(np.array(d)), 3)
+
+    def test_array_too_big(self):
+        # Test that array creation succeeds for arrays addressable by intp
+        # on the byte level and fails for too large arrays.
+        buf = np.zeros(100)
+
+        max_bytes = np.iinfo(np.intp).max
+        for dtype in ["intp", "S20", "b"]:
+            dtype = np.dtype(dtype)
+            itemsize = dtype.itemsize
+
+            np.ndarray(buffer=buf, strides=(0,),
+                       shape=(max_bytes//itemsize,), dtype=dtype)
+            assert_raises(ValueError, np.ndarray, buffer=buf, strides=(0,),
+                          shape=(max_bytes//itemsize + 1,), dtype=dtype)
+
+    def _ragged_creation(self, seq):
+        # without dtype=object, the ragged object raises
+        with pytest.raises(ValueError, match=".*detected shape was"):
+            a = np.array(seq)
+
+        return np.array(seq, dtype=object)
+
+    def test_ragged_ndim_object(self):
+        # Lists of mismatching depths are treated as object arrays
+        a = self._ragged_creation([[1], 2, 3])
+        assert_equal(a.shape, (3,))
+        assert_equal(a.dtype, object)
+
+        a = self._ragged_creation([1, [2], 3])
+        assert_equal(a.shape, (3,))
+        assert_equal(a.dtype, object)
+
+        a = self._ragged_creation([1, 2, [3]])
+        assert_equal(a.shape, (3,))
+        assert_equal(a.dtype, object)
+
+    def test_ragged_shape_object(self):
+        # The ragged dimension of a list is turned into an object array
+        a = self._ragged_creation([[1, 1], [2], [3]])
+        assert_equal(a.shape, (3,))
+        assert_equal(a.dtype, object)
+
+        a = self._ragged_creation([[1], [2, 2], [3]])
+        assert_equal(a.shape, (3,))
+        assert_equal(a.dtype, object)
+
+        a = self._ragged_creation([[1], [2], [3, 3]])
+        assert a.shape == (3,)
+        assert a.dtype == object
+
+    def test_array_of_ragged_array(self):
+        outer = np.array([None, None])
+        outer[0] = outer[1] = np.array([1, 2, 3])
+        assert np.array(outer).shape == (2,)
+        assert np.array([outer]).shape == (1, 2)
+
+        outer_ragged = np.array([None, None])
+        outer_ragged[0] = np.array([1, 2, 3])
+        outer_ragged[1] = np.array([1, 2, 3, 4])
+        # should both of these emit deprecation warnings?
+        assert np.array(outer_ragged).shape == (2,)
+        assert np.array([outer_ragged]).shape == (1, 2,)
+
+    def test_deep_nonragged_object(self):
+        # None of these should raise, even though they are missing dtype=object
+        a = np.array([[[Decimal(1)]]])
+        a = np.array([1, Decimal(1)])
+        a = np.array([[1], [Decimal(1)]])
+
+    @pytest.mark.parametrize("dtype", [object, "O,O", "O,(3)O", "(2,3)O"])
+    @pytest.mark.parametrize("function", [
+            np.ndarray, np.empty,
+            lambda shape, dtype: np.empty_like(np.empty(shape, dtype=dtype))])
+    def test_object_initialized_to_None(self, function, dtype):
+        # NumPy has support for object fields to be NULL (meaning None)
+        # but generally, we should always fill with the proper None, and
+        # downstream may rely on that.  (For fully initialized arrays!)
+        arr = function(3, dtype=dtype)
+        # We expect a fill value of None, which is not NULL:
+        expected = np.array(None).tobytes()
+        expected = expected * (arr.nbytes // len(expected))
+        assert arr.tobytes() == expected
+
+    @pytest.mark.parametrize("func", [
+        np.array, np.asarray, np.asanyarray, np.ascontiguousarray,
+        np.asfortranarray])
+    def test_creation_from_dtypemeta(self, func):
+        dtype = np.dtype('i')
+        arr1 = func([1, 2, 3], dtype=dtype)
+        arr2 = func([1, 2, 3], dtype=type(dtype))
+        assert_array_equal(arr1, arr2)
+        assert arr2.dtype == dtype
+
+
+class TestStructured:
+    def test_subarray_field_access(self):
+        a = np.zeros((3, 5), dtype=[('a', ('i4', (2, 2)))])
+        a['a'] = np.arange(60).reshape(3, 5, 2, 2)
+
+        # Since the subarray is always in C-order, a transpose
+        # does not swap the subarray:
+        assert_array_equal(a.T['a'], a['a'].transpose(1, 0, 2, 3))
+
+        # In Fortran order, the subarray gets appended
+        # like in all other cases, not prepended as a special case
+        b = a.copy(order='F')
+        assert_equal(a['a'].shape, b['a'].shape)
+        assert_equal(a.T['a'].shape, a.T.copy()['a'].shape)
+
+    def test_subarray_comparison(self):
+        # Check that comparisons between record arrays with
+        # multi-dimensional field types work properly
+        a = np.rec.fromrecords(
+            [([1, 2, 3], 'a', [[1, 2], [3, 4]]), ([3, 3, 3], 'b', [[0, 0], [0, 0]])],
+            dtype=[('a', ('f4', 3)), ('b', object), ('c', ('i4', (2, 2)))])
+        b = a.copy()
+        assert_equal(a == b, [True, True])
+        assert_equal(a != b, [False, False])
+        b[1].b = 'c'
+        assert_equal(a == b, [True, False])
+        assert_equal(a != b, [False, True])
+        for i in range(3):
+            b[0].a = a[0].a
+            b[0].a[i] = 5
+            assert_equal(a == b, [False, False])
+            assert_equal(a != b, [True, True])
+        for i in range(2):
+            for j in range(2):
+                b = a.copy()
+                b[0].c[i, j] = 10
+                assert_equal(a == b, [False, True])
+                assert_equal(a != b, [True, False])
+
+        # Check that broadcasting with a subarray works, including cases that
+        # require promotion to work:
+        a = np.array([[(0,)], [(1,)]], dtype=[('a', 'f8')])
+        b = np.array([(0,), (0,), (1,)], dtype=[('a', 'f8')])
+        assert_equal(a == b, [[True, True, False], [False, False, True]])
+        assert_equal(b == a, [[True, True, False], [False, False, True]])
+        a = np.array([[(0,)], [(1,)]], dtype=[('a', 'f8', (1,))])
+        b = np.array([(0,), (0,), (1,)], dtype=[('a', 'f8', (1,))])
+        assert_equal(a == b, [[True, True, False], [False, False, True]])
+        assert_equal(b == a, [[True, True, False], [False, False, True]])
+        a = np.array([[([0, 0],)], [([1, 1],)]], dtype=[('a', 'f8', (2,))])
+        b = np.array([([0, 0],), ([0, 1],), ([1, 1],)], dtype=[('a', 'f8', (2,))])
+        assert_equal(a == b, [[True, False, False], [False, False, True]])
+        assert_equal(b == a, [[True, False, False], [False, False, True]])
+
+        # Check that broadcasting Fortran-style arrays with a subarray work
+        a = np.array([[([0, 0],)], [([1, 1],)]], dtype=[('a', 'f8', (2,))], order='F')
+        b = np.array([([0, 0],), ([0, 1],), ([1, 1],)], dtype=[('a', 'f8', (2,))])
+        assert_equal(a == b, [[True, False, False], [False, False, True]])
+        assert_equal(b == a, [[True, False, False], [False, False, True]])
+
+        # Check that incompatible sub-array shapes don't result to broadcasting
+        x = np.zeros((1,), dtype=[('a', ('f4', (1, 2))), ('b', 'i1')])
+        y = np.zeros((1,), dtype=[('a', ('f4', (2,))), ('b', 'i1')])
+        # The main importance is that it does not return True:
+        with pytest.raises(TypeError):
+            x == y
+
+        x = np.zeros((1,), dtype=[('a', ('f4', (2, 1))), ('b', 'i1')])
+        y = np.zeros((1,), dtype=[('a', ('f4', (2,))), ('b', 'i1')])
+        # The main importance is that it does not return True:
+        with pytest.raises(TypeError):
+            x == y
+
+    def test_empty_structured_array_comparison(self):
+        # Check that comparison works on empty arrays with nontrivially
+        # shaped fields
+        a = np.zeros(0, [('a', '<f8', (1, 1))])
+        assert_equal(a, a)
+        a = np.zeros(0, [('a', '<f8', (1,))])
+        assert_equal(a, a)
+        a = np.zeros((0, 0), [('a', '<f8', (1, 1))])
+        assert_equal(a, a)
+        a = np.zeros((1, 0, 1), [('a', '<f8', (1, 1))])
+        assert_equal(a, a)
+
+    @pytest.mark.parametrize("op", [operator.eq, operator.ne])
+    def test_structured_array_comparison_bad_broadcasts(self, op):
+        a = np.zeros(3, dtype='i,i')
+        b = np.array([], dtype="i,i")
+        with pytest.raises(ValueError):
+            op(a, b)
+
+    def test_structured_comparisons_with_promotion(self):
+        # Check that structured arrays can be compared so long as their
+        # dtypes promote fine:
+        a = np.array([(5, 42), (10, 1)], dtype=[('a', '>i8'), ('b', '<f8')])
+        b = np.array([(5, 43), (10, 1)], dtype=[('a', '<i8'), ('b', '>f8')])
+        assert_equal(a == b, [False, True])
+        assert_equal(a != b, [True, False])
+
+        a = np.array([(5, 42), (10, 1)], dtype=[('a', '>f8'), ('b', '<f8')])
+        b = np.array([(5, 43), (10, 1)], dtype=[('a', '<i8'), ('b', '>i8')])
+        assert_equal(a == b, [False, True])
+        assert_equal(a != b, [True, False])
+
+        # Including with embedded subarray dtype (although subarray comparison
+        # itself may still be a bit weird and compare the raw data)
+        a = np.array([(5, 42), (10, 1)], dtype=[('a', '10>f8'), ('b', '5<f8')])
+        b = np.array([(5, 43), (10, 1)], dtype=[('a', '10<i8'), ('b', '5>i8')])
+        assert_equal(a == b, [False, True])
+        assert_equal(a != b, [True, False])
+
+    @pytest.mark.parametrize("op", [
+            operator.eq, lambda x, y: operator.eq(y, x),
+            operator.ne, lambda x, y: operator.ne(y, x)])
+    def test_void_comparison_failures(self, op):
+        # In principle, one could decide to return an array of False for some
+        # if comparisons are impossible.  But right now we return TypeError
+        # when "void" dtype are involved.
+        x = np.zeros(3, dtype=[('a', 'i1')])
+        y = np.zeros(3)
+        # Cannot compare non-structured to structured:
+        with pytest.raises(TypeError):
+            op(x, y)
+
+        # Added title prevents promotion, but casts are OK:
+        y = np.zeros(3, dtype=[(('title', 'a'), 'i1')])
+        assert np.can_cast(y.dtype, x.dtype)
+        with pytest.raises(TypeError):
+            op(x, y)
+
+        x = np.zeros(3, dtype="V7")
+        y = np.zeros(3, dtype="V8")
+        with pytest.raises(TypeError):
+            op(x, y)
+
+    def test_casting(self):
+        # Check that casting a structured array to change its byte order
+        # works
+        a = np.array([(1,)], dtype=[('a', '<i4')])
+        assert_(np.can_cast(a.dtype, [('a', '>i4')], casting='unsafe'))
+        b = a.astype([('a', '>i4')])
+        assert_equal(b, a.byteswap().newbyteorder())
+        assert_equal(a['a'][0], b['a'][0])
+
+        # Check that equality comparison works on structured arrays if
+        # they are 'equiv'-castable
+        a = np.array([(5, 42), (10, 1)], dtype=[('a', '>i4'), ('b', '<f8')])
+        b = np.array([(5, 42), (10, 1)], dtype=[('a', '<i4'), ('b', '>f8')])
+        assert_(np.can_cast(a.dtype, b.dtype, casting='equiv'))
+        assert_equal(a == b, [True, True])
+
+        # Check that 'equiv' casting can change byte order
+        assert_(np.can_cast(a.dtype, b.dtype, casting='equiv'))
+        c = a.astype(b.dtype, casting='equiv')
+        assert_equal(a == c, [True, True])
+
+        # Check that 'safe' casting can change byte order and up-cast
+        # fields
+        t = [('a', '<i8'), ('b', '>f8')]
+        assert_(np.can_cast(a.dtype, t, casting='safe'))
+        c = a.astype(t, casting='safe')
+        assert_equal((c == np.array([(5, 42), (10, 1)], dtype=t)),
+                     [True, True])
+
+        # Check that 'same_kind' casting can change byte order and
+        # change field widths within a "kind"
+        t = [('a', '<i4'), ('b', '>f4')]
+        assert_(np.can_cast(a.dtype, t, casting='same_kind'))
+        c = a.astype(t, casting='same_kind')
+        assert_equal((c == np.array([(5, 42), (10, 1)], dtype=t)),
+                     [True, True])
+
+        # Check that casting fails if the casting rule should fail on
+        # any of the fields
+        t = [('a', '>i8'), ('b', '<f4')]
+        assert_(not np.can_cast(a.dtype, t, casting='safe'))
+        assert_raises(TypeError, a.astype, t, casting='safe')
+        t = [('a', '>i2'), ('b', '<f8')]
+        assert_(not np.can_cast(a.dtype, t, casting='equiv'))
+        assert_raises(TypeError, a.astype, t, casting='equiv')
+        t = [('a', '>i8'), ('b', '<i2')]
+        assert_(not np.can_cast(a.dtype, t, casting='same_kind'))
+        assert_raises(TypeError, a.astype, t, casting='same_kind')
+        assert_(not np.can_cast(a.dtype, b.dtype, casting='no'))
+        assert_raises(TypeError, a.astype, b.dtype, casting='no')
+
+        # Check that non-'unsafe' casting can't change the set of field names
+        for casting in ['no', 'safe', 'equiv', 'same_kind']:
+            t = [('a', '>i4')]
+            assert_(not np.can_cast(a.dtype, t, casting=casting))
+            t = [('a', '>i4'), ('b', '<f8'), ('c', 'i4')]
+            assert_(not np.can_cast(a.dtype, t, casting=casting))
+
+    def test_objview(self):
+        # https://github.com/numpy/numpy/issues/3286
+        a = np.array([], dtype=[('a', 'f'), ('b', 'f'), ('c', 'O')])
+        a[['a', 'b']]  # TypeError?
+
+        # https://github.com/numpy/numpy/issues/3253
+        dat2 = np.zeros(3, [('A', 'i'), ('B', '|O')])
+        dat2[['B', 'A']]  # TypeError?
+
+    def test_setfield(self):
+        # https://github.com/numpy/numpy/issues/3126
+        struct_dt = np.dtype([('elem', 'i4', 5),])
+        dt = np.dtype([('field', 'i4', 10),('struct', struct_dt)])
+        x = np.zeros(1, dt)
+        x[0]['field'] = np.ones(10, dtype='i4')
+        x[0]['struct'] = np.ones(1, dtype=struct_dt)
+        assert_equal(x[0]['field'], np.ones(10, dtype='i4'))
+
+    def test_setfield_object(self):
+        # make sure object field assignment with ndarray value
+        # on void scalar mimics setitem behavior
+        b = np.zeros(1, dtype=[('x', 'O')])
+        # next line should work identically to b['x'][0] = np.arange(3)
+        b[0]['x'] = np.arange(3)
+        assert_equal(b[0]['x'], np.arange(3))
+
+        # check that broadcasting check still works
+        c = np.zeros(1, dtype=[('x', 'O', 5)])
+
+        def testassign():
+            c[0]['x'] = np.arange(3)
+
+        assert_raises(ValueError, testassign)
+
+    def test_zero_width_string(self):
+        # Test for PR #6430 / issues #473, #4955, #2585
+
+        dt = np.dtype([('I', int), ('S', 'S0')])
+
+        x = np.zeros(4, dtype=dt)
+
+        assert_equal(x['S'], [b'', b'', b'', b''])
+        assert_equal(x['S'].itemsize, 0)
+
+        x['S'] = ['a', 'b', 'c', 'd']
+        assert_equal(x['S'], [b'', b'', b'', b''])
+        assert_equal(x['I'], [0, 0, 0, 0])
+
+        # Variation on test case from #4955
+        x['S'][x['I'] == 0] = 'hello'
+        assert_equal(x['S'], [b'', b'', b'', b''])
+        assert_equal(x['I'], [0, 0, 0, 0])
+
+        # Variation on test case from #2585
+        x['S'] = 'A'
+        assert_equal(x['S'], [b'', b'', b'', b''])
+        assert_equal(x['I'], [0, 0, 0, 0])
+
+        # Allow zero-width dtypes in ndarray constructor
+        y = np.ndarray(4, dtype=x['S'].dtype)
+        assert_equal(y.itemsize, 0)
+        assert_equal(x['S'], y)
+
+        # More tests for indexing an array with zero-width fields
+        assert_equal(np.zeros(4, dtype=[('a', 'S0,S0'),
+                                        ('b', 'u1')])['a'].itemsize, 0)
+        assert_equal(np.empty(3, dtype='S0,S0').itemsize, 0)
+        assert_equal(np.zeros(4, dtype='S0,u1')['f0'].itemsize, 0)
+
+        xx = x['S'].reshape((2, 2))
+        assert_equal(xx.itemsize, 0)
+        assert_equal(xx, [[b'', b''], [b'', b'']])
+        # check for no uninitialized memory due to viewing S0 array
+        assert_equal(xx[:].dtype, xx.dtype)
+        assert_array_equal(eval(repr(xx), dict(array=np.array)), xx)
+
+        b = io.BytesIO()
+        np.save(b, xx)
+
+        b.seek(0)
+        yy = np.load(b)
+        assert_equal(yy.itemsize, 0)
+        assert_equal(xx, yy)
+
+        with temppath(suffix='.npy') as tmp:
+            np.save(tmp, xx)
+            yy = np.load(tmp)
+            assert_equal(yy.itemsize, 0)
+            assert_equal(xx, yy)
+
+    def test_base_attr(self):
+        a = np.zeros(3, dtype='i4,f4')
+        b = a[0]
+        assert_(b.base is a)
+
+    def test_assignment(self):
+        def testassign(arr, v):
+            c = arr.copy()
+            c[0] = v  # assign using setitem
+            c[1:] = v # assign using "dtype_transfer" code paths
+            return c
+
+        dt = np.dtype([('foo', 'i8'), ('bar', 'i8')])
+        arr = np.ones(2, dt)
+        v1 = np.array([(2,3)], dtype=[('foo', 'i8'), ('bar', 'i8')])
+        v2 = np.array([(2,3)], dtype=[('bar', 'i8'), ('foo', 'i8')])
+        v3 = np.array([(2,3)], dtype=[('bar', 'i8'), ('baz', 'i8')])
+        v4 = np.array([(2,)],  dtype=[('bar', 'i8')])
+        v5 = np.array([(2,3)], dtype=[('foo', 'f8'), ('bar', 'f8')])
+        w = arr.view({'names': ['bar'], 'formats': ['i8'], 'offsets': [8]})
+
+        ans = np.array([(2,3),(2,3)], dtype=dt)
+        assert_equal(testassign(arr, v1), ans)
+        assert_equal(testassign(arr, v2), ans)
+        assert_equal(testassign(arr, v3), ans)
+        assert_raises(TypeError, lambda: testassign(arr, v4))
+        assert_equal(testassign(arr, v5), ans)
+        w[:] = 4
+        assert_equal(arr, np.array([(1,4),(1,4)], dtype=dt))
+
+        # test field-reordering, assignment by position, and self-assignment
+        a = np.array([(1,2,3)],
+                     dtype=[('foo', 'i8'), ('bar', 'i8'), ('baz', 'f4')])
+        a[['foo', 'bar']] = a[['bar', 'foo']]
+        assert_equal(a[0].item(), (2,1,3))
+
+        # test that this works even for 'simple_unaligned' structs
+        # (ie, that PyArray_EquivTypes cares about field order too)
+        a = np.array([(1,2)], dtype=[('a', 'i4'), ('b', 'i4')])
+        a[['a', 'b']] = a[['b', 'a']]
+        assert_equal(a[0].item(), (2,1))
+
+    def test_scalar_assignment(self):
+        with assert_raises(ValueError):
+            arr = np.arange(25).reshape(5, 5)
+            arr.itemset(3)
+
+    def test_structuredscalar_indexing(self):
+        # test gh-7262
+        x = np.empty(shape=1, dtype="(2)3S,(2)3U")
+        assert_equal(x[["f0","f1"]][0], x[0][["f0","f1"]])
+        assert_equal(x[0], x[0][()])
+
+    def test_multiindex_titles(self):
+        a = np.zeros(4, dtype=[(('a', 'b'), 'i'), ('c', 'i'), ('d', 'i')])
+        assert_raises(KeyError, lambda : a[['a','c']])
+        assert_raises(KeyError, lambda : a[['a','a']])
+        assert_raises(ValueError, lambda : a[['b','b']])  # field exists, but repeated
+        a[['b','c']]  # no exception
+
+    def test_structured_cast_promotion_fieldorder(self):
+        # gh-15494
+        # dtypes with different field names are not promotable
+        A = ("a", "<i8")
+        B = ("b", ">i8")
+        ab = np.array([(1, 2)], dtype=[A, B])
+        ba = np.array([(1, 2)], dtype=[B, A])
+        assert_raises(TypeError, np.concatenate, ab, ba)
+        assert_raises(TypeError, np.result_type, ab.dtype, ba.dtype)
+        assert_raises(TypeError, np.promote_types, ab.dtype, ba.dtype)
+
+        # dtypes with same field names/order but different memory offsets
+        # and byte-order are promotable to packed nbo.
+        assert_equal(np.promote_types(ab.dtype, ba[['a', 'b']].dtype),
+                     repack_fields(ab.dtype.newbyteorder('N')))
+
+        # gh-13667
+        # dtypes with different fieldnames but castable field types are castable
+        assert_equal(np.can_cast(ab.dtype, ba.dtype), True)
+        assert_equal(ab.astype(ba.dtype).dtype, ba.dtype)
+        assert_equal(np.can_cast('f8,i8', [('f0', 'f8'), ('f1', 'i8')]), True)
+        assert_equal(np.can_cast('f8,i8', [('f1', 'f8'), ('f0', 'i8')]), True)
+        assert_equal(np.can_cast('f8,i8', [('f1', 'i8'), ('f0', 'f8')]), False)
+        assert_equal(np.can_cast('f8,i8', [('f1', 'i8'), ('f0', 'f8')],
+                                 casting='unsafe'), True)
+
+        ab[:] = ba  # make sure assignment still works
+
+        # tests of type-promotion of corresponding fields
+        dt1 = np.dtype([("", "i4")])
+        dt2 = np.dtype([("", "i8")])
+        assert_equal(np.promote_types(dt1, dt2), np.dtype([('f0', 'i8')]))
+        assert_equal(np.promote_types(dt2, dt1), np.dtype([('f0', 'i8')]))
+        assert_raises(TypeError, np.promote_types, dt1, np.dtype([("", "V3")]))
+        assert_equal(np.promote_types('i4,f8', 'i8,f4'),
+                     np.dtype([('f0', 'i8'), ('f1', 'f8')]))
+        # test nested case
+        dt1nest = np.dtype([("", dt1)])
+        dt2nest = np.dtype([("", dt2)])
+        assert_equal(np.promote_types(dt1nest, dt2nest),
+                     np.dtype([('f0', np.dtype([('f0', 'i8')]))]))
+
+        # note that offsets are lost when promoting:
+        dt = np.dtype({'names': ['x'], 'formats': ['i4'], 'offsets': [8]})
+        a = np.ones(3, dtype=dt)
+        assert_equal(np.concatenate([a, a]).dtype, np.dtype([('x', 'i4')]))
+
+    @pytest.mark.parametrize("dtype_dict", [
+            dict(names=["a", "b"], formats=["i4", "f"], itemsize=100),
+            dict(names=["a", "b"], formats=["i4", "f"],
+                 offsets=[0, 12])])
+    @pytest.mark.parametrize("align", [True, False])
+    def test_structured_promotion_packs(self, dtype_dict, align):
+        # Structured dtypes are packed when promoted (we consider the packed
+        # form to be "canonical"), so tere is no extra padding.
+        dtype = np.dtype(dtype_dict, align=align)
+        # Remove non "canonical" dtype options:
+        dtype_dict.pop("itemsize", None)
+        dtype_dict.pop("offsets", None)
+        expected = np.dtype(dtype_dict, align=align)
+
+        res = np.promote_types(dtype, dtype)
+        assert res.itemsize == expected.itemsize
+        assert res.fields == expected.fields
+
+        # But the "expected" one, should just be returned unchanged:
+        res = np.promote_types(expected, expected)
+        assert res is expected
+
+    def test_structured_asarray_is_view(self):
+        # A scalar viewing an array preserves its view even when creating a
+        # new array. This test documents behaviour, it may not be the best
+        # desired behaviour.
+        arr = np.array([1], dtype="i,i")
+        scalar = arr[0]
+        assert not scalar.flags.owndata  # view into the array
+        assert np.asarray(scalar).base is scalar
+        # But never when a dtype is passed in:
+        assert np.asarray(scalar, dtype=scalar.dtype).base is None
+        # A scalar which owns its data does not have this property.
+        # It is not easy to create one, one method is to use pickle:
+        scalar = pickle.loads(pickle.dumps(scalar))
+        assert scalar.flags.owndata
+        assert np.asarray(scalar).base is None
+
+class TestBool:
+    def test_test_interning(self):
+        a0 = np.bool_(0)
+        b0 = np.bool_(False)
+        assert_(a0 is b0)
+        a1 = np.bool_(1)
+        b1 = np.bool_(True)
+        assert_(a1 is b1)
+        assert_(np.array([True])[0] is a1)
+        assert_(np.array(True)[()] is a1)
+
+    def test_sum(self):
+        d = np.ones(101, dtype=bool)
+        assert_equal(d.sum(), d.size)
+        assert_equal(d[::2].sum(), d[::2].size)
+        assert_equal(d[::-2].sum(), d[::-2].size)
+
+        d = np.frombuffer(b'\xff\xff' * 100, dtype=bool)
+        assert_equal(d.sum(), d.size)
+        assert_equal(d[::2].sum(), d[::2].size)
+        assert_equal(d[::-2].sum(), d[::-2].size)
+
+    def check_count_nonzero(self, power, length):
+        powers = [2 ** i for i in range(length)]
+        for i in range(2**power):
+            l = [(i & x) != 0 for x in powers]
+            a = np.array(l, dtype=bool)
+            c = builtins.sum(l)
+            assert_equal(np.count_nonzero(a), c)
+            av = a.view(np.uint8)
+            av *= 3
+            assert_equal(np.count_nonzero(a), c)
+            av *= 4
+            assert_equal(np.count_nonzero(a), c)
+            av[av != 0] = 0xFF
+            assert_equal(np.count_nonzero(a), c)
+
+    def test_count_nonzero(self):
+        # check all 12 bit combinations in a length 17 array
+        # covers most cases of the 16 byte unrolled code
+        self.check_count_nonzero(12, 17)
+
+    @pytest.mark.slow
+    def test_count_nonzero_all(self):
+        # check all combinations in a length 17 array
+        # covers all cases of the 16 byte unrolled code
+        self.check_count_nonzero(17, 17)
+
+    def test_count_nonzero_unaligned(self):
+        # prevent mistakes as e.g. gh-4060
+        for o in range(7):
+            a = np.zeros((18,), dtype=bool)[o+1:]
+            a[:o] = True
+            assert_equal(np.count_nonzero(a), builtins.sum(a.tolist()))
+            a = np.ones((18,), dtype=bool)[o+1:]
+            a[:o] = False
+            assert_equal(np.count_nonzero(a), builtins.sum(a.tolist()))
+
+    def _test_cast_from_flexible(self, dtype):
+        # empty string -> false
+        for n in range(3):
+            v = np.array(b'', (dtype, n))
+            assert_equal(bool(v), False)
+            assert_equal(bool(v[()]), False)
+            assert_equal(v.astype(bool), False)
+            assert_(isinstance(v.astype(bool), np.ndarray))
+            assert_(v[()].astype(bool) is np.False_)
+
+        # anything else -> true
+        for n in range(1, 4):
+            for val in [b'a', b'0', b' ']:
+                v = np.array(val, (dtype, n))
+                assert_equal(bool(v), True)
+                assert_equal(bool(v[()]), True)
+                assert_equal(v.astype(bool), True)
+                assert_(isinstance(v.astype(bool), np.ndarray))
+                assert_(v[()].astype(bool) is np.True_)
+
+    def test_cast_from_void(self):
+        self._test_cast_from_flexible(np.void)
+
+    @pytest.mark.xfail(reason="See gh-9847")
+    def test_cast_from_unicode(self):
+        self._test_cast_from_flexible(np.str_)
+
+    @pytest.mark.xfail(reason="See gh-9847")
+    def test_cast_from_bytes(self):
+        self._test_cast_from_flexible(np.bytes_)
+
+
+class TestZeroSizeFlexible:
+    @staticmethod
+    def _zeros(shape, dtype=str):
+        dtype = np.dtype(dtype)
+        if dtype == np.void:
+            return np.zeros(shape, dtype=(dtype, 0))
+
+        # not constructable directly
+        dtype = np.dtype([('x', dtype, 0)])
+        return np.zeros(shape, dtype=dtype)['x']
+
+    def test_create(self):
+        zs = self._zeros(10, bytes)
+        assert_equal(zs.itemsize, 0)
+        zs = self._zeros(10, np.void)
+        assert_equal(zs.itemsize, 0)
+        zs = self._zeros(10, str)
+        assert_equal(zs.itemsize, 0)
+
+    def _test_sort_partition(self, name, kinds, **kwargs):
+        # Previously, these would all hang
+        for dt in [bytes, np.void, str]:
+            zs = self._zeros(10, dt)
+            sort_method = getattr(zs, name)
+            sort_func = getattr(np, name)
+            for kind in kinds:
+                sort_method(kind=kind, **kwargs)
+                sort_func(zs, kind=kind, **kwargs)
+
+    def test_sort(self):
+        self._test_sort_partition('sort', kinds='qhs')
+
+    def test_argsort(self):
+        self._test_sort_partition('argsort', kinds='qhs')
+
+    def test_partition(self):
+        self._test_sort_partition('partition', kinds=['introselect'], kth=2)
+
+    def test_argpartition(self):
+        self._test_sort_partition('argpartition', kinds=['introselect'], kth=2)
+
+    def test_resize(self):
+        # previously an error
+        for dt in [bytes, np.void, str]:
+            zs = self._zeros(10, dt)
+            zs.resize(25)
+            zs.resize((10, 10))
+
+    def test_view(self):
+        for dt in [bytes, np.void, str]:
+            zs = self._zeros(10, dt)
+
+            # viewing as itself should be allowed
+            assert_equal(zs.view(dt).dtype, np.dtype(dt))
+
+            # viewing as any non-empty type gives an empty result
+            assert_equal(zs.view((dt, 1)).shape, (0,))
+
+    def test_dumps(self):
+        zs = self._zeros(10, int)
+        assert_equal(zs, pickle.loads(zs.dumps()))
+
+    def test_pickle(self):
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            for dt in [bytes, np.void, str]:
+                zs = self._zeros(10, dt)
+                p = pickle.dumps(zs, protocol=proto)
+                zs2 = pickle.loads(p)
+
+                assert_equal(zs.dtype, zs2.dtype)
+
+    def test_pickle_empty(self):
+        """Checking if an empty array pickled and un-pickled will not cause a
+        segmentation fault"""
+        arr = np.array([]).reshape(999999, 0)
+        pk_dmp = pickle.dumps(arr)
+        pk_load = pickle.loads(pk_dmp)
+
+        assert pk_load.size == 0
+
+    @pytest.mark.skipif(pickle.HIGHEST_PROTOCOL < 5,
+                        reason="requires pickle protocol 5")
+    def test_pickle_with_buffercallback(self):
+        array = np.arange(10)
+        buffers = []
+        bytes_string = pickle.dumps(array, buffer_callback=buffers.append,
+                                    protocol=5)
+        array_from_buffer = pickle.loads(bytes_string, buffers=buffers)
+        # when using pickle protocol 5 with buffer callbacks,
+        # array_from_buffer is reconstructed from a buffer holding a view
+        # to the initial array's data, so modifying an element in array
+        # should modify it in array_from_buffer too.
+        array[0] = -1
+        assert array_from_buffer[0] == -1, array_from_buffer[0]
+
+
+class TestMethods:
+
+    sort_kinds = ['quicksort', 'heapsort', 'stable']
+
+    def test_all_where(self):
+        a = np.array([[True, False, True],
+                      [False, False, False],
+                      [True, True, True]])
+        wh_full = np.array([[True, False, True],
+                            [False, False, False],
+                            [True, False, True]])
+        wh_lower = np.array([[False],
+                             [False],
+                             [True]])
+        for _ax in [0, None]:
+            assert_equal(a.all(axis=_ax, where=wh_lower),
+                        np.all(a[wh_lower[:,0],:], axis=_ax))
+            assert_equal(np.all(a, axis=_ax, where=wh_lower),
+                         a[wh_lower[:,0],:].all(axis=_ax))
+
+        assert_equal(a.all(where=wh_full), True)
+        assert_equal(np.all(a, where=wh_full), True)
+        assert_equal(a.all(where=False), True)
+        assert_equal(np.all(a, where=False), True)
+
+    def test_any_where(self):
+        a = np.array([[True, False, True],
+                      [False, False, False],
+                      [True, True, True]])
+        wh_full = np.array([[False, True, False],
+                            [True, True, True],
+                            [False, False, False]])
+        wh_middle = np.array([[False],
+                              [True],
+                              [False]])
+        for _ax in [0, None]:
+            assert_equal(a.any(axis=_ax, where=wh_middle),
+                         np.any(a[wh_middle[:,0],:], axis=_ax))
+            assert_equal(np.any(a, axis=_ax, where=wh_middle),
+                         a[wh_middle[:,0],:].any(axis=_ax))
+        assert_equal(a.any(where=wh_full), False)
+        assert_equal(np.any(a, where=wh_full), False)
+        assert_equal(a.any(where=False), False)
+        assert_equal(np.any(a, where=False), False)
+
+    def test_compress(self):
+        tgt = [[5, 6, 7, 8, 9]]
+        arr = np.arange(10).reshape(2, 5)
+        out = arr.compress([0, 1], axis=0)
+        assert_equal(out, tgt)
+
+        tgt = [[1, 3], [6, 8]]
+        out = arr.compress([0, 1, 0, 1, 0], axis=1)
+        assert_equal(out, tgt)
+
+        tgt = [[1], [6]]
+        arr = np.arange(10).reshape(2, 5)
+        out = arr.compress([0, 1], axis=1)
+        assert_equal(out, tgt)
+
+        arr = np.arange(10).reshape(2, 5)
+        out = arr.compress([0, 1])
+        assert_equal(out, 1)
+
+    def test_choose(self):
+        x = 2*np.ones((3,), dtype=int)
+        y = 3*np.ones((3,), dtype=int)
+        x2 = 2*np.ones((2, 3), dtype=int)
+        y2 = 3*np.ones((2, 3), dtype=int)
+        ind = np.array([0, 0, 1])
+
+        A = ind.choose((x, y))
+        assert_equal(A, [2, 2, 3])
+
+        A = ind.choose((x2, y2))
+        assert_equal(A, [[2, 2, 3], [2, 2, 3]])
+
+        A = ind.choose((x, y2))
+        assert_equal(A, [[2, 2, 3], [2, 2, 3]])
+
+        oned = np.ones(1)
+        # gh-12031, caused SEGFAULT
+        assert_raises(TypeError, oned.choose,np.void(0), [oned])
+
+        out = np.array(0)
+        ret = np.choose(np.array(1), [10, 20, 30], out=out)
+        assert out is ret
+        assert_equal(out[()], 20)
+
+        # gh-6272 check overlap on out
+        x = np.arange(5)
+        y = np.choose([0,0,0], [x[:3], x[:3], x[:3]], out=x[1:4], mode='wrap')
+        assert_equal(y, np.array([0, 1, 2]))
+
+    def test_prod(self):
+        ba = [1, 2, 10, 11, 6, 5, 4]
+        ba2 = [[1, 2, 3, 4], [5, 6, 7, 9], [10, 3, 4, 5]]
+
+        for ctype in [np.int16, np.uint16, np.int32, np.uint32,
+                      np.float32, np.float64, np.complex64, np.complex128]:
+            a = np.array(ba, ctype)
+            a2 = np.array(ba2, ctype)
+            if ctype in ['1', 'b']:
+                assert_raises(ArithmeticError, a.prod)
+                assert_raises(ArithmeticError, a2.prod, axis=1)
+            else:
+                assert_equal(a.prod(axis=0), 26400)
+                assert_array_equal(a2.prod(axis=0),
+                                   np.array([50, 36, 84, 180], ctype))
+                assert_array_equal(a2.prod(axis=-1),
+                                   np.array([24, 1890, 600], ctype))
+
+    @pytest.mark.parametrize('dtype', [None, object])
+    def test_repeat(self, dtype):
+        m = np.array([1, 2, 3, 4, 5, 6], dtype=dtype)
+        m_rect = m.reshape((2, 3))
+
+        A = m.repeat([1, 3, 2, 1, 1, 2])
+        assert_equal(A, [1, 2, 2, 2, 3,
+                         3, 4, 5, 6, 6])
+
+        A = m.repeat(2)
+        assert_equal(A, [1, 1, 2, 2, 3, 3,
+                         4, 4, 5, 5, 6, 6])
+
+        A = m_rect.repeat([2, 1], axis=0)
+        assert_equal(A, [[1, 2, 3],
+                         [1, 2, 3],
+                         [4, 5, 6]])
+
+        A = m_rect.repeat([1, 3, 2], axis=1)
+        assert_equal(A, [[1, 2, 2, 2, 3, 3],
+                         [4, 5, 5, 5, 6, 6]])
+
+        A = m_rect.repeat(2, axis=0)
+        assert_equal(A, [[1, 2, 3],
+                         [1, 2, 3],
+                         [4, 5, 6],
+                         [4, 5, 6]])
+
+        A = m_rect.repeat(2, axis=1)
+        assert_equal(A, [[1, 1, 2, 2, 3, 3],
+                         [4, 4, 5, 5, 6, 6]])
+
+    def test_reshape(self):
+        arr = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]])
+
+        tgt = [[1, 2, 3, 4, 5, 6], [7, 8, 9, 10, 11, 12]]
+        assert_equal(arr.reshape(2, 6), tgt)
+
+        tgt = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]]
+        assert_equal(arr.reshape(3, 4), tgt)
+
+        tgt = [[1, 10, 8, 6], [4, 2, 11, 9], [7, 5, 3, 12]]
+        assert_equal(arr.reshape((3, 4), order='F'), tgt)
+
+        tgt = [[1, 4, 7, 10], [2, 5, 8, 11], [3, 6, 9, 12]]
+        assert_equal(arr.T.reshape((3, 4), order='C'), tgt)
+
+    def test_round(self):
+        def check_round(arr, expected, *round_args):
+            assert_equal(arr.round(*round_args), expected)
+            # With output array
+            out = np.zeros_like(arr)
+            res = arr.round(*round_args, out=out)
+            assert_equal(out, expected)
+            assert out is res
+
+        check_round(np.array([1.2, 1.5]), [1, 2])
+        check_round(np.array(1.5), 2)
+        check_round(np.array([12.2, 15.5]), [10, 20], -1)
+        check_round(np.array([12.15, 15.51]), [12.2, 15.5], 1)
+        # Complex rounding
+        check_round(np.array([4.5 + 1.5j]), [4 + 2j])
+        check_round(np.array([12.5 + 15.5j]), [10 + 20j], -1)
+
+    def test_squeeze(self):
+        a = np.array([[[1], [2], [3]]])
+        assert_equal(a.squeeze(), [1, 2, 3])
+        assert_equal(a.squeeze(axis=(0,)), [[1], [2], [3]])
+        assert_raises(ValueError, a.squeeze, axis=(1,))
+        assert_equal(a.squeeze(axis=(2,)), [[1, 2, 3]])
+
+    def test_transpose(self):
+        a = np.array([[1, 2], [3, 4]])
+        assert_equal(a.transpose(), [[1, 3], [2, 4]])
+        assert_raises(ValueError, lambda: a.transpose(0))
+        assert_raises(ValueError, lambda: a.transpose(0, 0))
+        assert_raises(ValueError, lambda: a.transpose(0, 1, 2))
+
+    def test_sort(self):
+        # test ordering for floats and complex containing nans. It is only
+        # necessary to check the less-than comparison, so sorts that
+        # only follow the insertion sort path are sufficient. We only
+        # test doubles and complex doubles as the logic is the same.
+
+        # check doubles
+        msg = "Test real sort order with nans"
+        a = np.array([np.nan, 1, 0])
+        b = np.sort(a)
+        assert_equal(b, a[::-1], msg)
+        # check complex
+        msg = "Test complex sort order with nans"
+        a = np.zeros(9, dtype=np.complex128)
+        a.real += [np.nan, np.nan, np.nan, 1, 0, 1, 1, 0, 0]
+        a.imag += [np.nan, 1, 0, np.nan, np.nan, 1, 0, 1, 0]
+        b = np.sort(a)
+        assert_equal(b, a[::-1], msg)
+
+    # all c scalar sorts use the same code with different types
+    # so it suffices to run a quick check with one type. The number
+    # of sorted items must be greater than ~50 to check the actual
+    # algorithm because quick and merge sort fall over to insertion
+    # sort for small arrays.
+
+    @pytest.mark.parametrize('dtype', [np.uint8, np.uint16, np.uint32, np.uint64,
+                                       np.float16, np.float32, np.float64,
+                                       np.longdouble])
+    def test_sort_unsigned(self, dtype):
+        a = np.arange(101, dtype=dtype)
+        b = a[::-1].copy()
+        for kind in self.sort_kinds:
+            msg = "scalar sort, kind=%s" % kind
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+            c = b.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    @pytest.mark.parametrize('dtype',
+                             [np.int8, np.int16, np.int32, np.int64, np.float16,
+                              np.float32, np.float64, np.longdouble])
+    def test_sort_signed(self, dtype):
+        a = np.arange(-50, 51, dtype=dtype)
+        b = a[::-1].copy()
+        for kind in self.sort_kinds:
+            msg = "scalar sort, kind=%s" % (kind)
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+            c = b.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    @pytest.mark.parametrize('dtype', [np.float32, np.float64, np.longdouble])
+    @pytest.mark.parametrize('part', ['real', 'imag'])
+    def test_sort_complex(self, part, dtype):
+        # test complex sorts. These use the same code as the scalars
+        # but the compare function differs.
+        cdtype = {
+            np.single: np.csingle,
+            np.double: np.cdouble,
+            np.longdouble: np.clongdouble,
+        }[dtype]
+        a = np.arange(-50, 51, dtype=dtype)
+        b = a[::-1].copy()
+        ai = (a * (1+1j)).astype(cdtype)
+        bi = (b * (1+1j)).astype(cdtype)
+        setattr(ai, part, 1)
+        setattr(bi, part, 1)
+        for kind in self.sort_kinds:
+            msg = "complex sort, %s part == 1, kind=%s" % (part, kind)
+            c = ai.copy()
+            c.sort(kind=kind)
+            assert_equal(c, ai, msg)
+            c = bi.copy()
+            c.sort(kind=kind)
+            assert_equal(c, ai, msg)
+
+    def test_sort_complex_byte_swapping(self):
+        # test sorting of complex arrays requiring byte-swapping, gh-5441
+        for endianness in '<>':
+            for dt in np.typecodes['Complex']:
+                arr = np.array([1+3.j, 2+2.j, 3+1.j], dtype=endianness + dt)
+                c = arr.copy()
+                c.sort()
+                msg = 'byte-swapped complex sort, dtype={0}'.format(dt)
+                assert_equal(c, arr, msg)
+
+    @pytest.mark.parametrize('dtype', [np.bytes_, np.str_])
+    def test_sort_string(self, dtype):
+        # np.array will perform the encoding to bytes for us in the bytes test
+        a = np.array(['aaaaaaaa' + chr(i) for i in range(101)], dtype=dtype)
+        b = a[::-1].copy()
+        for kind in self.sort_kinds:
+            msg = "kind=%s" % kind
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+            c = b.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    def test_sort_object(self):
+        # test object array sorts.
+        a = np.empty((101,), dtype=object)
+        a[:] = list(range(101))
+        b = a[::-1]
+        for kind in ['q', 'h', 'm']:
+            msg = "kind=%s" % kind
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+            c = b.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    @pytest.mark.parametrize("dt", [
+            np.dtype([('f', float), ('i', int)]),
+            np.dtype([('f', float), ('i', object)])])
+    @pytest.mark.parametrize("step", [1, 2])
+    def test_sort_structured(self, dt, step):
+        # test record array sorts.
+        a = np.array([(i, i) for i in range(101*step)], dtype=dt)
+        b = a[::-1]
+        for kind in ['q', 'h', 'm']:
+            msg = "kind=%s" % kind
+            c = a.copy()[::step]
+            indx = c.argsort(kind=kind)
+            c.sort(kind=kind)
+            assert_equal(c, a[::step], msg)
+            assert_equal(a[::step][indx], a[::step], msg)
+            c = b.copy()[::step]
+            indx = c.argsort(kind=kind)
+            c.sort(kind=kind)
+            assert_equal(c, a[step-1::step], msg)
+            assert_equal(b[::step][indx], a[step-1::step], msg)
+
+    @pytest.mark.parametrize('dtype', ['datetime64[D]', 'timedelta64[D]'])
+    def test_sort_time(self, dtype):
+        # test datetime64 and timedelta64 sorts.
+        a = np.arange(0, 101, dtype=dtype)
+        b = a[::-1]
+        for kind in ['q', 'h', 'm']:
+            msg = "kind=%s" % kind
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+            c = b.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    def test_sort_axis(self):
+        # check axis handling. This should be the same for all type
+        # specific sorts, so we only check it for one type and one kind
+        a = np.array([[3, 2], [1, 0]])
+        b = np.array([[1, 0], [3, 2]])
+        c = np.array([[2, 3], [0, 1]])
+        d = a.copy()
+        d.sort(axis=0)
+        assert_equal(d, b, "test sort with axis=0")
+        d = a.copy()
+        d.sort(axis=1)
+        assert_equal(d, c, "test sort with axis=1")
+        d = a.copy()
+        d.sort()
+        assert_equal(d, c, "test sort with default axis")
+
+    def test_sort_size_0(self):
+        # check axis handling for multidimensional empty arrays
+        a = np.array([])
+        a.shape = (3, 2, 1, 0)
+        for axis in range(-a.ndim, a.ndim):
+            msg = 'test empty array sort with axis={0}'.format(axis)
+            assert_equal(np.sort(a, axis=axis), a, msg)
+        msg = 'test empty array sort with axis=None'
+        assert_equal(np.sort(a, axis=None), a.ravel(), msg)
+
+    def test_sort_bad_ordering(self):
+        # test generic class with bogus ordering,
+        # should not segfault.
+        class Boom:
+            def __lt__(self, other):
+                return True
+
+        a = np.array([Boom()] * 100, dtype=object)
+        for kind in self.sort_kinds:
+            msg = "kind=%s" % kind
+            c = a.copy()
+            c.sort(kind=kind)
+            assert_equal(c, a, msg)
+
+    def test_void_sort(self):
+        # gh-8210 - previously segfaulted
+        for i in range(4):
+            rand = np.random.randint(256, size=4000, dtype=np.uint8)
+            arr = rand.view('V4')
+            arr[::-1].sort()
+
+        dt = np.dtype([('val', 'i4', (1,))])
+        for i in range(4):
+            rand = np.random.randint(256, size=4000, dtype=np.uint8)
+            arr = rand.view(dt)
+            arr[::-1].sort()
+
+    def test_sort_raises(self):
+        #gh-9404
+        arr = np.array([0, datetime.now(), 1], dtype=object)
+        for kind in self.sort_kinds:
+            assert_raises(TypeError, arr.sort, kind=kind)
+        #gh-3879
+        class Raiser:
+            def raises_anything(*args, **kwargs):
+                raise TypeError("SOMETHING ERRORED")
+            __eq__ = __ne__ = __lt__ = __gt__ = __ge__ = __le__ = raises_anything
+        arr = np.array([[Raiser(), n] for n in range(10)]).reshape(-1)
+        np.random.shuffle(arr)
+        for kind in self.sort_kinds:
+            assert_raises(TypeError, arr.sort, kind=kind)
+
+    def test_sort_degraded(self):
+        # test degraded dataset would take minutes to run with normal qsort
+        d = np.arange(1000000)
+        do = d.copy()
+        x = d
+        # create a median of 3 killer where each median is the sorted second
+        # last element of the quicksort partition
+        while x.size > 3:
+            mid = x.size // 2
+            x[mid], x[-2] = x[-2], x[mid]
+            x = x[:-2]
+
+        assert_equal(np.sort(d), do)
+        assert_equal(d[np.argsort(d)], do)
+
+    def test_copy(self):
+        def assert_fortran(arr):
+            assert_(arr.flags.fortran)
+            assert_(arr.flags.f_contiguous)
+            assert_(not arr.flags.c_contiguous)
+
+        def assert_c(arr):
+            assert_(not arr.flags.fortran)
+            assert_(not arr.flags.f_contiguous)
+            assert_(arr.flags.c_contiguous)
+
+        a = np.empty((2, 2), order='F')
+        # Test copying a Fortran array
+        assert_c(a.copy())
+        assert_c(a.copy('C'))
+        assert_fortran(a.copy('F'))
+        assert_fortran(a.copy('A'))
+
+        # Now test starting with a C array.
+        a = np.empty((2, 2), order='C')
+        assert_c(a.copy())
+        assert_c(a.copy('C'))
+        assert_fortran(a.copy('F'))
+        assert_c(a.copy('A'))
+
+    @pytest.mark.parametrize("dtype", ['O', np.int32, 'i,O'])
+    def test__deepcopy__(self, dtype):
+        # Force the entry of NULLs into array
+        a = np.empty(4, dtype=dtype)
+        ctypes.memset(a.ctypes.data, 0, a.nbytes)
+
+        # Ensure no error is raised, see gh-21833
+        b = a.__deepcopy__({})
+
+        a[0] = 42
+        with pytest.raises(AssertionError):
+            assert_array_equal(a, b)
+
+    def test__deepcopy__catches_failure(self):
+        class MyObj:
+            def __deepcopy__(self, *args, **kwargs):
+                raise RuntimeError
+
+        arr = np.array([1, MyObj(), 3], dtype='O')
+        with pytest.raises(RuntimeError):
+            arr.__deepcopy__({})
+
+    def test_sort_order(self):
+        # Test sorting an array with fields
+        x1 = np.array([21, 32, 14])
+        x2 = np.array(['my', 'first', 'name'])
+        x3 = np.array([3.1, 4.5, 6.2])
+        r = np.rec.fromarrays([x1, x2, x3], names='id,word,number')
+
+        r.sort(order=['id'])
+        assert_equal(r.id, np.array([14, 21, 32]))
+        assert_equal(r.word, np.array(['name', 'my', 'first']))
+        assert_equal(r.number, np.array([6.2, 3.1, 4.5]))
+
+        r.sort(order=['word'])
+        assert_equal(r.id, np.array([32, 21, 14]))
+        assert_equal(r.word, np.array(['first', 'my', 'name']))
+        assert_equal(r.number, np.array([4.5, 3.1, 6.2]))
+
+        r.sort(order=['number'])
+        assert_equal(r.id, np.array([21, 32, 14]))
+        assert_equal(r.word, np.array(['my', 'first', 'name']))
+        assert_equal(r.number, np.array([3.1, 4.5, 6.2]))
+
+        assert_raises_regex(ValueError, 'duplicate',
+            lambda: r.sort(order=['id', 'id']))
+
+        if sys.byteorder == 'little':
+            strtype = '>i2'
+        else:
+            strtype = '<i2'
+        mydtype = [('name', 'U5'), ('col2', strtype)]
+        r = np.array([('a', 1), ('b', 255), ('c', 3), ('d', 258)],
+                     dtype=mydtype)
+        r.sort(order='col2')
+        assert_equal(r['col2'], [1, 3, 255, 258])
+        assert_equal(r, np.array([('a', 1), ('c', 3), ('b', 255), ('d', 258)],
+                                 dtype=mydtype))
+
+    def test_argsort(self):
+        # all c scalar argsorts use the same code with different types
+        # so it suffices to run a quick check with one type. The number
+        # of sorted items must be greater than ~50 to check the actual
+        # algorithm because quick and merge sort fall over to insertion
+        # sort for small arrays.
+
+        for dtype in [np.int32, np.uint32, np.float32]:
+            a = np.arange(101, dtype=dtype)
+            b = a[::-1].copy()
+            for kind in self.sort_kinds:
+                msg = "scalar argsort, kind=%s, dtype=%s" % (kind, dtype)
+                assert_equal(a.copy().argsort(kind=kind), a, msg)
+                assert_equal(b.copy().argsort(kind=kind), b, msg)
+
+        # test complex argsorts. These use the same code as the scalars
+        # but the compare function differs.
+        ai = a*1j + 1
+        bi = b*1j + 1
+        for kind in self.sort_kinds:
+            msg = "complex argsort, kind=%s" % kind
+            assert_equal(ai.copy().argsort(kind=kind), a, msg)
+            assert_equal(bi.copy().argsort(kind=kind), b, msg)
+        ai = a + 1j
+        bi = b + 1j
+        for kind in self.sort_kinds:
+            msg = "complex argsort, kind=%s" % kind
+            assert_equal(ai.copy().argsort(kind=kind), a, msg)
+            assert_equal(bi.copy().argsort(kind=kind), b, msg)
+
+        # test argsort of complex arrays requiring byte-swapping, gh-5441
+        for endianness in '<>':
+            for dt in np.typecodes['Complex']:
+                arr = np.array([1+3.j, 2+2.j, 3+1.j], dtype=endianness + dt)
+                msg = 'byte-swapped complex argsort, dtype={0}'.format(dt)
+                assert_equal(arr.argsort(),
+                             np.arange(len(arr), dtype=np.intp), msg)
+
+        # test string argsorts.
+        s = 'aaaaaaaa'
+        a = np.array([s + chr(i) for i in range(101)])
+        b = a[::-1].copy()
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in self.sort_kinds:
+            msg = "string argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # test unicode argsorts.
+        s = 'aaaaaaaa'
+        a = np.array([s + chr(i) for i in range(101)], dtype=np.str_)
+        b = a[::-1]
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in self.sort_kinds:
+            msg = "unicode argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # test object array argsorts.
+        a = np.empty((101,), dtype=object)
+        a[:] = list(range(101))
+        b = a[::-1]
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in self.sort_kinds:
+            msg = "object argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # test structured array argsorts.
+        dt = np.dtype([('f', float), ('i', int)])
+        a = np.array([(i, i) for i in range(101)], dtype=dt)
+        b = a[::-1]
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in self.sort_kinds:
+            msg = "structured array argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # test datetime64 argsorts.
+        a = np.arange(0, 101, dtype='datetime64[D]')
+        b = a[::-1]
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in ['q', 'h', 'm']:
+            msg = "datetime64 argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # test timedelta64 argsorts.
+        a = np.arange(0, 101, dtype='timedelta64[D]')
+        b = a[::-1]
+        r = np.arange(101)
+        rr = r[::-1]
+        for kind in ['q', 'h', 'm']:
+            msg = "timedelta64 argsort, kind=%s" % kind
+            assert_equal(a.copy().argsort(kind=kind), r, msg)
+            assert_equal(b.copy().argsort(kind=kind), rr, msg)
+
+        # check axis handling. This should be the same for all type
+        # specific argsorts, so we only check it for one type and one kind
+        a = np.array([[3, 2], [1, 0]])
+        b = np.array([[1, 1], [0, 0]])
+        c = np.array([[1, 0], [1, 0]])
+        assert_equal(a.copy().argsort(axis=0), b)
+        assert_equal(a.copy().argsort(axis=1), c)
+        assert_equal(a.copy().argsort(), c)
+
+        # check axis handling for multidimensional empty arrays
+        a = np.array([])
+        a.shape = (3, 2, 1, 0)
+        for axis in range(-a.ndim, a.ndim):
+            msg = 'test empty array argsort with axis={0}'.format(axis)
+            assert_equal(np.argsort(a, axis=axis),
+                         np.zeros_like(a, dtype=np.intp), msg)
+        msg = 'test empty array argsort with axis=None'
+        assert_equal(np.argsort(a, axis=None),
+                     np.zeros_like(a.ravel(), dtype=np.intp), msg)
+
+        # check that stable argsorts are stable
+        r = np.arange(100)
+        # scalars
+        a = np.zeros(100)
+        assert_equal(a.argsort(kind='m'), r)
+        # complex
+        a = np.zeros(100, dtype=complex)
+        assert_equal(a.argsort(kind='m'), r)
+        # string
+        a = np.array(['aaaaaaaaa' for i in range(100)])
+        assert_equal(a.argsort(kind='m'), r)
+        # unicode
+        a = np.array(['aaaaaaaaa' for i in range(100)], dtype=np.str_)
+        assert_equal(a.argsort(kind='m'), r)
+
+    def test_sort_unicode_kind(self):
+        d = np.arange(10)
+        k = b'\xc3\xa4'.decode("UTF8")
+        assert_raises(ValueError, d.sort, kind=k)
+        assert_raises(ValueError, d.argsort, kind=k)
+
+    @pytest.mark.parametrize('a', [
+        np.array([0, 1, np.nan], dtype=np.float16),
+        np.array([0, 1, np.nan], dtype=np.float32),
+        np.array([0, 1, np.nan]),
+    ])
+    def test_searchsorted_floats(self, a):
+        # test for floats arrays containing nans. Explicitly test
+        # half, single, and double precision floats to verify that
+        # the NaN-handling is correct.
+        msg = "Test real (%s) searchsorted with nans, side='l'" % a.dtype
+        b = a.searchsorted(a, side='left')
+        assert_equal(b, np.arange(3), msg)
+        msg = "Test real (%s) searchsorted with nans, side='r'" % a.dtype
+        b = a.searchsorted(a, side='right')
+        assert_equal(b, np.arange(1, 4), msg)
+        # check keyword arguments
+        a.searchsorted(v=1)
+        x = np.array([0, 1, np.nan], dtype='float32')
+        y = np.searchsorted(x, x[-1])
+        assert_equal(y, 2)
+
+    def test_searchsorted_complex(self):
+        # test for complex arrays containing nans.
+        # The search sorted routines use the compare functions for the
+        # array type, so this checks if that is consistent with the sort
+        # order.
+        # check double complex
+        a = np.zeros(9, dtype=np.complex128)
+        a.real += [0, 0, 1, 1, 0, 1, np.nan, np.nan, np.nan]
+        a.imag += [0, 1, 0, 1, np.nan, np.nan, 0, 1, np.nan]
+        msg = "Test complex searchsorted with nans, side='l'"
+        b = a.searchsorted(a, side='left')
+        assert_equal(b, np.arange(9), msg)
+        msg = "Test complex searchsorted with nans, side='r'"
+        b = a.searchsorted(a, side='right')
+        assert_equal(b, np.arange(1, 10), msg)
+        msg = "Test searchsorted with little endian, side='l'"
+        a = np.array([0, 128], dtype='<i4')
+        b = a.searchsorted(np.array(128, dtype='<i4'))
+        assert_equal(b, 1, msg)
+        msg = "Test searchsorted with big endian, side='l'"
+        a = np.array([0, 128], dtype='>i4')
+        b = a.searchsorted(np.array(128, dtype='>i4'))
+        assert_equal(b, 1, msg)
+
+    def test_searchsorted_n_elements(self):
+        # Check 0 elements
+        a = np.ones(0)
+        b = a.searchsorted([0, 1, 2], 'left')
+        assert_equal(b, [0, 0, 0])
+        b = a.searchsorted([0, 1, 2], 'right')
+        assert_equal(b, [0, 0, 0])
+        a = np.ones(1)
+        # Check 1 element
+        b = a.searchsorted([0, 1, 2], 'left')
+        assert_equal(b, [0, 0, 1])
+        b = a.searchsorted([0, 1, 2], 'right')
+        assert_equal(b, [0, 1, 1])
+        # Check all elements equal
+        a = np.ones(2)
+        b = a.searchsorted([0, 1, 2], 'left')
+        assert_equal(b, [0, 0, 2])
+        b = a.searchsorted([0, 1, 2], 'right')
+        assert_equal(b, [0, 2, 2])
+
+    def test_searchsorted_unaligned_array(self):
+        # Test searching unaligned array
+        a = np.arange(10)
+        aligned = np.empty(a.itemsize * a.size + 1, 'uint8')
+        unaligned = aligned[1:].view(a.dtype)
+        unaligned[:] = a
+        # Test searching unaligned array
+        b = unaligned.searchsorted(a, 'left')
+        assert_equal(b, a)
+        b = unaligned.searchsorted(a, 'right')
+        assert_equal(b, a + 1)
+        # Test searching for unaligned keys
+        b = a.searchsorted(unaligned, 'left')
+        assert_equal(b, a)
+        b = a.searchsorted(unaligned, 'right')
+        assert_equal(b, a + 1)
+
+    def test_searchsorted_resetting(self):
+        # Test smart resetting of binsearch indices
+        a = np.arange(5)
+        b = a.searchsorted([6, 5, 4], 'left')
+        assert_equal(b, [5, 5, 4])
+        b = a.searchsorted([6, 5, 4], 'right')
+        assert_equal(b, [5, 5, 5])
+
+    def test_searchsorted_type_specific(self):
+        # Test all type specific binary search functions
+        types = ''.join((np.typecodes['AllInteger'], np.typecodes['AllFloat'],
+                         np.typecodes['Datetime'], '?O'))
+        for dt in types:
+            if dt == 'M':
+                dt = 'M8[D]'
+            if dt == '?':
+                a = np.arange(2, dtype=dt)
+                out = np.arange(2)
+            else:
+                a = np.arange(0, 5, dtype=dt)
+                out = np.arange(5)
+            b = a.searchsorted(a, 'left')
+            assert_equal(b, out)
+            b = a.searchsorted(a, 'right')
+            assert_equal(b, out + 1)
+            # Test empty array, use a fresh array to get warnings in
+            # valgrind if access happens.
+            e = np.ndarray(shape=0, buffer=b'', dtype=dt)
+            b = e.searchsorted(a, 'left')
+            assert_array_equal(b, np.zeros(len(a), dtype=np.intp))
+            b = a.searchsorted(e, 'left')
+            assert_array_equal(b, np.zeros(0, dtype=np.intp))
+
+    def test_searchsorted_unicode(self):
+        # Test searchsorted on unicode strings.
+
+        # 1.6.1 contained a string length miscalculation in
+        # arraytypes.c.src:UNICODE_compare() which manifested as
+        # incorrect/inconsistent results from searchsorted.
+        a = np.array(['P:\\20x_dapi_cy3\\20x_dapi_cy3_20100185_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100186_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100187_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100189_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100190_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100191_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100192_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100193_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100194_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100195_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100196_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100197_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100198_1',
+                      'P:\\20x_dapi_cy3\\20x_dapi_cy3_20100199_1'],
+                     dtype=np.str_)
+        ind = np.arange(len(a))
+        assert_equal([a.searchsorted(v, 'left') for v in a], ind)
+        assert_equal([a.searchsorted(v, 'right') for v in a], ind + 1)
+        assert_equal([a.searchsorted(a[i], 'left') for i in ind], ind)
+        assert_equal([a.searchsorted(a[i], 'right') for i in ind], ind + 1)
+
+    def test_searchsorted_with_invalid_sorter(self):
+        a = np.array([5, 2, 1, 3, 4])
+        s = np.argsort(a)
+        assert_raises(TypeError, np.searchsorted, a, 0,
+                      sorter=np.array((1, (2, 3)), dtype=object))
+        assert_raises(TypeError, np.searchsorted, a, 0, sorter=[1.1])
+        assert_raises(ValueError, np.searchsorted, a, 0, sorter=[1, 2, 3, 4])
+        assert_raises(ValueError, np.searchsorted, a, 0, sorter=[1, 2, 3, 4, 5, 6])
+
+        # bounds check
+        assert_raises(ValueError, np.searchsorted, a, 4, sorter=[0, 1, 2, 3, 5])
+        assert_raises(ValueError, np.searchsorted, a, 0, sorter=[-1, 0, 1, 2, 3])
+        assert_raises(ValueError, np.searchsorted, a, 0, sorter=[4, 0, -1, 2, 3])
+
+    def test_searchsorted_with_sorter(self):
+        a = np.random.rand(300)
+        s = a.argsort()
+        b = np.sort(a)
+        k = np.linspace(0, 1, 20)
+        assert_equal(b.searchsorted(k), a.searchsorted(k, sorter=s))
+
+        a = np.array([0, 1, 2, 3, 5]*20)
+        s = a.argsort()
+        k = [0, 1, 2, 3, 5]
+        expected = [0, 20, 40, 60, 80]
+        assert_equal(a.searchsorted(k, side='left', sorter=s), expected)
+        expected = [20, 40, 60, 80, 100]
+        assert_equal(a.searchsorted(k, side='right', sorter=s), expected)
+
+        # Test searching unaligned array
+        keys = np.arange(10)
+        a = keys.copy()
+        np.random.shuffle(s)
+        s = a.argsort()
+        aligned = np.empty(a.itemsize * a.size + 1, 'uint8')
+        unaligned = aligned[1:].view(a.dtype)
+        # Test searching unaligned array
+        unaligned[:] = a
+        b = unaligned.searchsorted(keys, 'left', s)
+        assert_equal(b, keys)
+        b = unaligned.searchsorted(keys, 'right', s)
+        assert_equal(b, keys + 1)
+        # Test searching for unaligned keys
+        unaligned[:] = keys
+        b = a.searchsorted(unaligned, 'left', s)
+        assert_equal(b, keys)
+        b = a.searchsorted(unaligned, 'right', s)
+        assert_equal(b, keys + 1)
+
+        # Test all type specific indirect binary search functions
+        types = ''.join((np.typecodes['AllInteger'], np.typecodes['AllFloat'],
+                         np.typecodes['Datetime'], '?O'))
+        for dt in types:
+            if dt == 'M':
+                dt = 'M8[D]'
+            if dt == '?':
+                a = np.array([1, 0], dtype=dt)
+                # We want the sorter array to be of a type that is different
+                # from np.intp in all platforms, to check for #4698
+                s = np.array([1, 0], dtype=np.int16)
+                out = np.array([1, 0])
+            else:
+                a = np.array([3, 4, 1, 2, 0], dtype=dt)
+                # We want the sorter array to be of a type that is different
+                # from np.intp in all platforms, to check for #4698
+                s = np.array([4, 2, 3, 0, 1], dtype=np.int16)
+                out = np.array([3, 4, 1, 2, 0], dtype=np.intp)
+            b = a.searchsorted(a, 'left', s)
+            assert_equal(b, out)
+            b = a.searchsorted(a, 'right', s)
+            assert_equal(b, out + 1)
+            # Test empty array, use a fresh array to get warnings in
+            # valgrind if access happens.
+            e = np.ndarray(shape=0, buffer=b'', dtype=dt)
+            b = e.searchsorted(a, 'left', s[:0])
+            assert_array_equal(b, np.zeros(len(a), dtype=np.intp))
+            b = a.searchsorted(e, 'left', s)
+            assert_array_equal(b, np.zeros(0, dtype=np.intp))
+
+        # Test non-contiguous sorter array
+        a = np.array([3, 4, 1, 2, 0])
+        srt = np.empty((10,), dtype=np.intp)
+        srt[1::2] = -1
+        srt[::2] = [4, 2, 3, 0, 1]
+        s = srt[::2]
+        out = np.array([3, 4, 1, 2, 0], dtype=np.intp)
+        b = a.searchsorted(a, 'left', s)
+        assert_equal(b, out)
+        b = a.searchsorted(a, 'right', s)
+        assert_equal(b, out + 1)
+
+    def test_searchsorted_return_type(self):
+        # Functions returning indices should always return base ndarrays
+        class A(np.ndarray):
+            pass
+        a = np.arange(5).view(A)
+        b = np.arange(1, 3).view(A)
+        s = np.arange(5).view(A)
+        assert_(not isinstance(a.searchsorted(b, 'left'), A))
+        assert_(not isinstance(a.searchsorted(b, 'right'), A))
+        assert_(not isinstance(a.searchsorted(b, 'left', s), A))
+        assert_(not isinstance(a.searchsorted(b, 'right', s), A))
+
+    @pytest.mark.parametrize("dtype", np.typecodes["All"])
+    def test_argpartition_out_of_range(self, dtype):
+        # Test out of range values in kth raise an error, gh-5469
+        d = np.arange(10).astype(dtype=dtype)
+        assert_raises(ValueError, d.argpartition, 10)
+        assert_raises(ValueError, d.argpartition, -11)
+
+    @pytest.mark.parametrize("dtype", np.typecodes["All"])
+    def test_partition_out_of_range(self, dtype):
+        # Test out of range values in kth raise an error, gh-5469
+        d = np.arange(10).astype(dtype=dtype)
+        assert_raises(ValueError, d.partition, 10)
+        assert_raises(ValueError, d.partition, -11)
+
+    def test_argpartition_integer(self):
+        # Test non-integer values in kth raise an error/
+        d = np.arange(10)
+        assert_raises(TypeError, d.argpartition, 9.)
+        # Test also for generic type argpartition, which uses sorting
+        # and used to not bound check kth
+        d_obj = np.arange(10, dtype=object)
+        assert_raises(TypeError, d_obj.argpartition, 9.)
+
+    def test_partition_integer(self):
+        # Test out of range values in kth raise an error, gh-5469
+        d = np.arange(10)
+        assert_raises(TypeError, d.partition, 9.)
+        # Test also for generic type partition, which uses sorting
+        # and used to not bound check kth
+        d_obj = np.arange(10, dtype=object)
+        assert_raises(TypeError, d_obj.partition, 9.)
+
+    @pytest.mark.parametrize("kth_dtype", np.typecodes["AllInteger"])
+    def test_partition_empty_array(self, kth_dtype):
+        # check axis handling for multidimensional empty arrays
+        kth = np.array(0, dtype=kth_dtype)[()]
+        a = np.array([])
+        a.shape = (3, 2, 1, 0)
+        for axis in range(-a.ndim, a.ndim):
+            msg = 'test empty array partition with axis={0}'.format(axis)
+            assert_equal(np.partition(a, kth, axis=axis), a, msg)
+        msg = 'test empty array partition with axis=None'
+        assert_equal(np.partition(a, kth, axis=None), a.ravel(), msg)
+
+    @pytest.mark.parametrize("kth_dtype", np.typecodes["AllInteger"])
+    def test_argpartition_empty_array(self, kth_dtype):
+        # check axis handling for multidimensional empty arrays
+        kth = np.array(0, dtype=kth_dtype)[()]
+        a = np.array([])
+        a.shape = (3, 2, 1, 0)
+        for axis in range(-a.ndim, a.ndim):
+            msg = 'test empty array argpartition with axis={0}'.format(axis)
+            assert_equal(np.partition(a, kth, axis=axis),
+                         np.zeros_like(a, dtype=np.intp), msg)
+        msg = 'test empty array argpartition with axis=None'
+        assert_equal(np.partition(a, kth, axis=None),
+                     np.zeros_like(a.ravel(), dtype=np.intp), msg)
+
+    def test_partition(self):
+        d = np.arange(10)
+        assert_raises(TypeError, np.partition, d, 2, kind=1)
+        assert_raises(ValueError, np.partition, d, 2, kind="nonsense")
+        assert_raises(ValueError, np.argpartition, d, 2, kind="nonsense")
+        assert_raises(ValueError, d.partition, 2, axis=0, kind="nonsense")
+        assert_raises(ValueError, d.argpartition, 2, axis=0, kind="nonsense")
+        for k in ("introselect",):
+            d = np.array([])
+            assert_array_equal(np.partition(d, 0, kind=k), d)
+            assert_array_equal(np.argpartition(d, 0, kind=k), d)
+            d = np.ones(1)
+            assert_array_equal(np.partition(d, 0, kind=k)[0], d)
+            assert_array_equal(d[np.argpartition(d, 0, kind=k)],
+                               np.partition(d, 0, kind=k))
+
+            # kth not modified
+            kth = np.array([30, 15, 5])
+            okth = kth.copy()
+            np.partition(np.arange(40), kth)
+            assert_array_equal(kth, okth)
+
+            for r in ([2, 1], [1, 2], [1, 1]):
+                d = np.array(r)
+                tgt = np.sort(d)
+                assert_array_equal(np.partition(d, 0, kind=k)[0], tgt[0])
+                assert_array_equal(np.partition(d, 1, kind=k)[1], tgt[1])
+                assert_array_equal(d[np.argpartition(d, 0, kind=k)],
+                                   np.partition(d, 0, kind=k))
+                assert_array_equal(d[np.argpartition(d, 1, kind=k)],
+                                   np.partition(d, 1, kind=k))
+                for i in range(d.size):
+                    d[i:].partition(0, kind=k)
+                assert_array_equal(d, tgt)
+
+            for r in ([3, 2, 1], [1, 2, 3], [2, 1, 3], [2, 3, 1],
+                      [1, 1, 1], [1, 2, 2], [2, 2, 1], [1, 2, 1]):
+                d = np.array(r)
+                tgt = np.sort(d)
+                assert_array_equal(np.partition(d, 0, kind=k)[0], tgt[0])
+                assert_array_equal(np.partition(d, 1, kind=k)[1], tgt[1])
+                assert_array_equal(np.partition(d, 2, kind=k)[2], tgt[2])
+                assert_array_equal(d[np.argpartition(d, 0, kind=k)],
+                                   np.partition(d, 0, kind=k))
+                assert_array_equal(d[np.argpartition(d, 1, kind=k)],
+                                   np.partition(d, 1, kind=k))
+                assert_array_equal(d[np.argpartition(d, 2, kind=k)],
+                                   np.partition(d, 2, kind=k))
+                for i in range(d.size):
+                    d[i:].partition(0, kind=k)
+                assert_array_equal(d, tgt)
+
+            d = np.ones(50)
+            assert_array_equal(np.partition(d, 0, kind=k), d)
+            assert_array_equal(d[np.argpartition(d, 0, kind=k)],
+                               np.partition(d, 0, kind=k))
+
+            # sorted
+            d = np.arange(49)
+            assert_equal(np.partition(d, 5, kind=k)[5], 5)
+            assert_equal(np.partition(d, 15, kind=k)[15], 15)
+            assert_array_equal(d[np.argpartition(d, 5, kind=k)],
+                               np.partition(d, 5, kind=k))
+            assert_array_equal(d[np.argpartition(d, 15, kind=k)],
+                               np.partition(d, 15, kind=k))
+
+            # rsorted
+            d = np.arange(47)[::-1]
+            assert_equal(np.partition(d, 6, kind=k)[6], 6)
+            assert_equal(np.partition(d, 16, kind=k)[16], 16)
+            assert_array_equal(d[np.argpartition(d, 6, kind=k)],
+                               np.partition(d, 6, kind=k))
+            assert_array_equal(d[np.argpartition(d, 16, kind=k)],
+                               np.partition(d, 16, kind=k))
+
+            assert_array_equal(np.partition(d, -6, kind=k),
+                               np.partition(d, 41, kind=k))
+            assert_array_equal(np.partition(d, -16, kind=k),
+                               np.partition(d, 31, kind=k))
+            assert_array_equal(d[np.argpartition(d, -6, kind=k)],
+                               np.partition(d, 41, kind=k))
+
+            # median of 3 killer, O(n^2) on pure median 3 pivot quickselect
+            # exercises the median of median of 5 code used to keep O(n)
+            d = np.arange(1000000)
+            x = np.roll(d, d.size // 2)
+            mid = x.size // 2 + 1
+            assert_equal(np.partition(x, mid)[mid], mid)
+            d = np.arange(1000001)
+            x = np.roll(d, d.size // 2 + 1)
+            mid = x.size // 2 + 1
+            assert_equal(np.partition(x, mid)[mid], mid)
+
+            # max
+            d = np.ones(10)
+            d[1] = 4
+            assert_equal(np.partition(d, (2, -1))[-1], 4)
+            assert_equal(np.partition(d, (2, -1))[2], 1)
+            assert_equal(d[np.argpartition(d, (2, -1))][-1], 4)
+            assert_equal(d[np.argpartition(d, (2, -1))][2], 1)
+            d[1] = np.nan
+            assert_(np.isnan(d[np.argpartition(d, (2, -1))][-1]))
+            assert_(np.isnan(np.partition(d, (2, -1))[-1]))
+
+            # equal elements
+            d = np.arange(47) % 7
+            tgt = np.sort(np.arange(47) % 7)
+            np.random.shuffle(d)
+            for i in range(d.size):
+                assert_equal(np.partition(d, i, kind=k)[i], tgt[i])
+            assert_array_equal(d[np.argpartition(d, 6, kind=k)],
+                               np.partition(d, 6, kind=k))
+            assert_array_equal(d[np.argpartition(d, 16, kind=k)],
+                               np.partition(d, 16, kind=k))
+            for i in range(d.size):
+                d[i:].partition(0, kind=k)
+            assert_array_equal(d, tgt)
+
+            d = np.array([0, 1, 2, 3, 4, 5, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+                          7, 7, 7, 7, 7, 9])
+            kth = [0, 3, 19, 20]
+            assert_equal(np.partition(d, kth, kind=k)[kth], (0, 3, 7, 7))
+            assert_equal(d[np.argpartition(d, kth, kind=k)][kth], (0, 3, 7, 7))
+
+            d = np.array([2, 1])
+            d.partition(0, kind=k)
+            assert_raises(ValueError, d.partition, 2)
+            assert_raises(np.AxisError, d.partition, 3, axis=1)
+            assert_raises(ValueError, np.partition, d, 2)
+            assert_raises(np.AxisError, np.partition, d, 2, axis=1)
+            assert_raises(ValueError, d.argpartition, 2)
+            assert_raises(np.AxisError, d.argpartition, 3, axis=1)
+            assert_raises(ValueError, np.argpartition, d, 2)
+            assert_raises(np.AxisError, np.argpartition, d, 2, axis=1)
+            d = np.arange(10).reshape((2, 5))
+            d.partition(1, axis=0, kind=k)
+            d.partition(4, axis=1, kind=k)
+            np.partition(d, 1, axis=0, kind=k)
+            np.partition(d, 4, axis=1, kind=k)
+            np.partition(d, 1, axis=None, kind=k)
+            np.partition(d, 9, axis=None, kind=k)
+            d.argpartition(1, axis=0, kind=k)
+            d.argpartition(4, axis=1, kind=k)
+            np.argpartition(d, 1, axis=0, kind=k)
+            np.argpartition(d, 4, axis=1, kind=k)
+            np.argpartition(d, 1, axis=None, kind=k)
+            np.argpartition(d, 9, axis=None, kind=k)
+            assert_raises(ValueError, d.partition, 2, axis=0)
+            assert_raises(ValueError, d.partition, 11, axis=1)
+            assert_raises(TypeError, d.partition, 2, axis=None)
+            assert_raises(ValueError, np.partition, d, 9, axis=1)
+            assert_raises(ValueError, np.partition, d, 11, axis=None)
+            assert_raises(ValueError, d.argpartition, 2, axis=0)
+            assert_raises(ValueError, d.argpartition, 11, axis=1)
+            assert_raises(ValueError, np.argpartition, d, 9, axis=1)
+            assert_raises(ValueError, np.argpartition, d, 11, axis=None)
+
+            td = [(dt, s) for dt in [np.int32, np.float32, np.complex64]
+                  for s in (9, 16)]
+            for dt, s in td:
+                aae = assert_array_equal
+                at = assert_
+
+                d = np.arange(s, dtype=dt)
+                np.random.shuffle(d)
+                d1 = np.tile(np.arange(s, dtype=dt), (4, 1))
+                map(np.random.shuffle, d1)
+                d0 = np.transpose(d1)
+                for i in range(d.size):
+                    p = np.partition(d, i, kind=k)
+                    assert_equal(p[i], i)
+                    # all before are smaller
+                    assert_array_less(p[:i], p[i])
+                    # all after are larger
+                    assert_array_less(p[i], p[i + 1:])
+                    aae(p, d[np.argpartition(d, i, kind=k)])
+
+                    p = np.partition(d1, i, axis=1, kind=k)
+                    aae(p[:, i], np.array([i] * d1.shape[0], dtype=dt))
+                    # array_less does not seem to work right
+                    at((p[:, :i].T <= p[:, i]).all(),
+                       msg="%d: %r <= %r" % (i, p[:, i], p[:, :i].T))
+                    at((p[:, i + 1:].T > p[:, i]).all(),
+                       msg="%d: %r < %r" % (i, p[:, i], p[:, i + 1:].T))
+                    aae(p, d1[np.arange(d1.shape[0])[:, None],
+                        np.argpartition(d1, i, axis=1, kind=k)])
+
+                    p = np.partition(d0, i, axis=0, kind=k)
+                    aae(p[i, :], np.array([i] * d1.shape[0], dtype=dt))
+                    # array_less does not seem to work right
+                    at((p[:i, :] <= p[i, :]).all(),
+                       msg="%d: %r <= %r" % (i, p[i, :], p[:i, :]))
+                    at((p[i + 1:, :] > p[i, :]).all(),
+                       msg="%d: %r < %r" % (i, p[i, :], p[:, i + 1:]))
+                    aae(p, d0[np.argpartition(d0, i, axis=0, kind=k),
+                        np.arange(d0.shape[1])[None, :]])
+
+                    # check inplace
+                    dc = d.copy()
+                    dc.partition(i, kind=k)
+                    assert_equal(dc, np.partition(d, i, kind=k))
+                    dc = d0.copy()
+                    dc.partition(i, axis=0, kind=k)
+                    assert_equal(dc, np.partition(d0, i, axis=0, kind=k))
+                    dc = d1.copy()
+                    dc.partition(i, axis=1, kind=k)
+                    assert_equal(dc, np.partition(d1, i, axis=1, kind=k))
+
+    def assert_partitioned(self, d, kth):
+        prev = 0
+        for k in np.sort(kth):
+            assert_array_less(d[prev:k], d[k], err_msg='kth %d' % k)
+            assert_((d[k:] >= d[k]).all(),
+                    msg="kth %d, %r not greater equal %d" % (k, d[k:], d[k]))
+            prev = k + 1
+
+    def test_partition_iterative(self):
+            d = np.arange(17)
+            kth = (0, 1, 2, 429, 231)
+            assert_raises(ValueError, d.partition, kth)
+            assert_raises(ValueError, d.argpartition, kth)
+            d = np.arange(10).reshape((2, 5))
+            assert_raises(ValueError, d.partition, kth, axis=0)
+            assert_raises(ValueError, d.partition, kth, axis=1)
+            assert_raises(ValueError, np.partition, d, kth, axis=1)
+            assert_raises(ValueError, np.partition, d, kth, axis=None)
+
+            d = np.array([3, 4, 2, 1])
+            p = np.partition(d, (0, 3))
+            self.assert_partitioned(p, (0, 3))
+            self.assert_partitioned(d[np.argpartition(d, (0, 3))], (0, 3))
+
+            assert_array_equal(p, np.partition(d, (-3, -1)))
+            assert_array_equal(p, d[np.argpartition(d, (-3, -1))])
+
+            d = np.arange(17)
+            np.random.shuffle(d)
+            d.partition(range(d.size))
+            assert_array_equal(np.arange(17), d)
+            np.random.shuffle(d)
+            assert_array_equal(np.arange(17), d[d.argpartition(range(d.size))])
+
+            # test unsorted kth
+            d = np.arange(17)
+            np.random.shuffle(d)
+            keys = np.array([1, 3, 8, -2])
+            np.random.shuffle(d)
+            p = np.partition(d, keys)
+            self.assert_partitioned(p, keys)
+            p = d[np.argpartition(d, keys)]
+            self.assert_partitioned(p, keys)
+            np.random.shuffle(keys)
+            assert_array_equal(np.partition(d, keys), p)
+            assert_array_equal(d[np.argpartition(d, keys)], p)
+
+            # equal kth
+            d = np.arange(20)[::-1]
+            self.assert_partitioned(np.partition(d, [5]*4), [5])
+            self.assert_partitioned(np.partition(d, [5]*4 + [6, 13]),
+                                    [5]*4 + [6, 13])
+            self.assert_partitioned(d[np.argpartition(d, [5]*4)], [5])
+            self.assert_partitioned(d[np.argpartition(d, [5]*4 + [6, 13])],
+                                    [5]*4 + [6, 13])
+
+            d = np.arange(12)
+            np.random.shuffle(d)
+            d1 = np.tile(np.arange(12), (4, 1))
+            map(np.random.shuffle, d1)
+            d0 = np.transpose(d1)
+
+            kth = (1, 6, 7, -1)
+            p = np.partition(d1, kth, axis=1)
+            pa = d1[np.arange(d1.shape[0])[:, None],
+                    d1.argpartition(kth, axis=1)]
+            assert_array_equal(p, pa)
+            for i in range(d1.shape[0]):
+                self.assert_partitioned(p[i,:], kth)
+            p = np.partition(d0, kth, axis=0)
+            pa = d0[np.argpartition(d0, kth, axis=0),
+                    np.arange(d0.shape[1])[None,:]]
+            assert_array_equal(p, pa)
+            for i in range(d0.shape[1]):
+                self.assert_partitioned(p[:, i], kth)
+
+    def test_partition_cdtype(self):
+        d = np.array([('Galahad', 1.7, 38), ('Arthur', 1.8, 41),
+                   ('Lancelot', 1.9, 38)],
+                  dtype=[('name', '|S10'), ('height', '<f8'), ('age', '<i4')])
+
+        tgt = np.sort(d, order=['age', 'height'])
+        assert_array_equal(np.partition(d, range(d.size),
+                                        order=['age', 'height']),
+                           tgt)
+        assert_array_equal(d[np.argpartition(d, range(d.size),
+                                             order=['age', 'height'])],
+                           tgt)
+        for k in range(d.size):
+            assert_equal(np.partition(d, k, order=['age', 'height'])[k],
+                        tgt[k])
+            assert_equal(d[np.argpartition(d, k, order=['age', 'height'])][k],
+                         tgt[k])
+
+        d = np.array(['Galahad', 'Arthur', 'zebra', 'Lancelot'])
+        tgt = np.sort(d)
+        assert_array_equal(np.partition(d, range(d.size)), tgt)
+        for k in range(d.size):
+            assert_equal(np.partition(d, k)[k], tgt[k])
+            assert_equal(d[np.argpartition(d, k)][k], tgt[k])
+
+    def test_partition_unicode_kind(self):
+        d = np.arange(10)
+        k = b'\xc3\xa4'.decode("UTF8")
+        assert_raises(ValueError, d.partition, 2, kind=k)
+        assert_raises(ValueError, d.argpartition, 2, kind=k)
+
+    def test_partition_fuzz(self):
+        # a few rounds of random data testing
+        for j in range(10, 30):
+            for i in range(1, j - 2):
+                d = np.arange(j)
+                np.random.shuffle(d)
+                d = d % np.random.randint(2, 30)
+                idx = np.random.randint(d.size)
+                kth = [0, idx, i, i + 1]
+                tgt = np.sort(d)[kth]
+                assert_array_equal(np.partition(d, kth)[kth], tgt,
+                                   err_msg="data: %r\n kth: %r" % (d, kth))
+
+    @pytest.mark.parametrize("kth_dtype", np.typecodes["AllInteger"])
+    def test_argpartition_gh5524(self, kth_dtype):
+        #  A test for functionality of argpartition on lists.
+        kth = np.array(1, dtype=kth_dtype)[()]
+        d = [6, 7, 3, 2, 9, 0]
+        p = np.argpartition(d, kth)
+        self.assert_partitioned(np.array(d)[p],[1])
+
+    def test_flatten(self):
+        x0 = np.array([[1, 2, 3], [4, 5, 6]], np.int32)
+        x1 = np.array([[[1, 2], [3, 4]], [[5, 6], [7, 8]]], np.int32)
+        y0 = np.array([1, 2, 3, 4, 5, 6], np.int32)
+        y0f = np.array([1, 4, 2, 5, 3, 6], np.int32)
+        y1 = np.array([1, 2, 3, 4, 5, 6, 7, 8], np.int32)
+        y1f = np.array([1, 5, 3, 7, 2, 6, 4, 8], np.int32)
+        assert_equal(x0.flatten(), y0)
+        assert_equal(x0.flatten('F'), y0f)
+        assert_equal(x0.flatten('F'), x0.T.flatten())
+        assert_equal(x1.flatten(), y1)
+        assert_equal(x1.flatten('F'), y1f)
+        assert_equal(x1.flatten('F'), x1.T.flatten())
+
+
+    @pytest.mark.parametrize('func', (np.dot, np.matmul))
+    def test_arr_mult(self, func):
+        a = np.array([[1, 0], [0, 1]])
+        b = np.array([[0, 1], [1, 0]])
+        c = np.array([[9, 1], [1, -9]])
+        d = np.arange(24).reshape(4, 6)
+        ddt = np.array(
+            [[  55,  145,  235,  325],
+             [ 145,  451,  757, 1063],
+             [ 235,  757, 1279, 1801],
+             [ 325, 1063, 1801, 2539]]
+        )
+        dtd = np.array(
+            [[504, 540, 576, 612, 648, 684],
+             [540, 580, 620, 660, 700, 740],
+             [576, 620, 664, 708, 752, 796],
+             [612, 660, 708, 756, 804, 852],
+             [648, 700, 752, 804, 856, 908],
+             [684, 740, 796, 852, 908, 964]]
+        )
+
+
+        # gemm vs syrk optimizations
+        for et in [np.float32, np.float64, np.complex64, np.complex128]:
+            eaf = a.astype(et)
+            assert_equal(func(eaf, eaf), eaf)
+            assert_equal(func(eaf.T, eaf), eaf)
+            assert_equal(func(eaf, eaf.T), eaf)
+            assert_equal(func(eaf.T, eaf.T), eaf)
+            assert_equal(func(eaf.T.copy(), eaf), eaf)
+            assert_equal(func(eaf, eaf.T.copy()), eaf)
+            assert_equal(func(eaf.T.copy(), eaf.T.copy()), eaf)
+
+        # syrk validations
+        for et in [np.float32, np.float64, np.complex64, np.complex128]:
+            eaf = a.astype(et)
+            ebf = b.astype(et)
+            assert_equal(func(ebf, ebf), eaf)
+            assert_equal(func(ebf.T, ebf), eaf)
+            assert_equal(func(ebf, ebf.T), eaf)
+            assert_equal(func(ebf.T, ebf.T), eaf)
+
+        # syrk - different shape, stride, and view validations
+        for et in [np.float32, np.float64, np.complex64, np.complex128]:
+            edf = d.astype(et)
+            assert_equal(
+                func(edf[::-1, :], edf.T),
+                func(edf[::-1, :].copy(), edf.T.copy())
+            )
+            assert_equal(
+                func(edf[:, ::-1], edf.T),
+                func(edf[:, ::-1].copy(), edf.T.copy())
+            )
+            assert_equal(
+                func(edf, edf[::-1, :].T),
+                func(edf, edf[::-1, :].T.copy())
+            )
+            assert_equal(
+                func(edf, edf[:, ::-1].T),
+                func(edf, edf[:, ::-1].T.copy())
+            )
+            assert_equal(
+                func(edf[:edf.shape[0] // 2, :], edf[::2, :].T),
+                func(edf[:edf.shape[0] // 2, :].copy(), edf[::2, :].T.copy())
+            )
+            assert_equal(
+                func(edf[::2, :], edf[:edf.shape[0] // 2, :].T),
+                func(edf[::2, :].copy(), edf[:edf.shape[0] // 2, :].T.copy())
+            )
+
+        # syrk - different shape
+        for et in [np.float32, np.float64, np.complex64, np.complex128]:
+            edf = d.astype(et)
+            eddtf = ddt.astype(et)
+            edtdf = dtd.astype(et)
+            assert_equal(func(edf, edf.T), eddtf)
+            assert_equal(func(edf.T, edf), edtdf)
+
+    @pytest.mark.parametrize('func', (np.dot, np.matmul))
+    @pytest.mark.parametrize('dtype', 'ifdFD')
+    def test_no_dgemv(self, func, dtype):
+        # check vector arg for contiguous before gemv
+        # gh-12156
+        a = np.arange(8.0, dtype=dtype).reshape(2, 4)
+        b = np.broadcast_to(1., (4, 1))
+        ret1 = func(a, b)
+        ret2 = func(a, b.copy())
+        assert_equal(ret1, ret2)
+
+        ret1 = func(b.T, a.T)
+        ret2 = func(b.T.copy(), a.T)
+        assert_equal(ret1, ret2)
+
+        # check for unaligned data
+        dt = np.dtype(dtype)
+        a = np.zeros(8 * dt.itemsize // 2 + 1, dtype='int16')[1:].view(dtype)
+        a = a.reshape(2, 4)
+        b = a[0]
+        # make sure it is not aligned
+        assert_(a.__array_interface__['data'][0] % dt.itemsize != 0)
+        ret1 = func(a, b)
+        ret2 = func(a.copy(), b.copy())
+        assert_equal(ret1, ret2)
+
+        ret1 = func(b.T, a.T)
+        ret2 = func(b.T.copy(), a.T.copy())
+        assert_equal(ret1, ret2)
+
+    def test_dot(self):
+        a = np.array([[1, 0], [0, 1]])
+        b = np.array([[0, 1], [1, 0]])
+        c = np.array([[9, 1], [1, -9]])
+        # function versus methods
+        assert_equal(np.dot(a, b), a.dot(b))
+        assert_equal(np.dot(np.dot(a, b), c), a.dot(b).dot(c))
+
+        # test passing in an output array
+        c = np.zeros_like(a)
+        a.dot(b, c)
+        assert_equal(c, np.dot(a, b))
+
+        # test keyword args
+        c = np.zeros_like(a)
+        a.dot(b=b, out=c)
+        assert_equal(c, np.dot(a, b))
+
+    def test_dot_type_mismatch(self):
+        c = 1.
+        A = np.array((1,1), dtype='i,i')
+
+        assert_raises(TypeError, np.dot, c, A)
+        assert_raises(TypeError, np.dot, A, c)
+
+    def test_dot_out_mem_overlap(self):
+        np.random.seed(1)
+
+        # Test BLAS and non-BLAS code paths, including all dtypes
+        # that dot() supports
+        dtypes = [np.dtype(code) for code in np.typecodes['All']
+                  if code not in 'USVM']
+        for dtype in dtypes:
+            a = np.random.rand(3, 3).astype(dtype)
+
+            # Valid dot() output arrays must be aligned
+            b = _aligned_zeros((3, 3), dtype=dtype)
+            b[...] = np.random.rand(3, 3)
+
+            y = np.dot(a, b)
+            x = np.dot(a, b, out=b)
+            assert_equal(x, y, err_msg=repr(dtype))
+
+            # Check invalid output array
+            assert_raises(ValueError, np.dot, a, b, out=b[::2])
+            assert_raises(ValueError, np.dot, a, b, out=b.T)
+
+    def test_dot_matmul_out(self):
+        # gh-9641
+        class Sub(np.ndarray):
+            pass
+        a = np.ones((2, 2)).view(Sub)
+        b = np.ones((2, 2)).view(Sub)
+        out = np.ones((2, 2))
+
+        # make sure out can be any ndarray (not only subclass of inputs)
+        np.dot(a, b, out=out)
+        np.matmul(a, b, out=out)
+
+    def test_dot_matmul_inner_array_casting_fails(self):
+
+        class A:
+            def __array__(self, *args, **kwargs):
+                raise NotImplementedError
+
+        # Don't override the error from calling __array__()
+        assert_raises(NotImplementedError, np.dot, A(), A())
+        assert_raises(NotImplementedError, np.matmul, A(), A())
+        assert_raises(NotImplementedError, np.inner, A(), A())
+
+    def test_matmul_out(self):
+        # overlapping memory
+        a = np.arange(18).reshape(2, 3, 3)
+        b = np.matmul(a, a)
+        c = np.matmul(a, a, out=a)
+        assert_(c is a)
+        assert_equal(c, b)
+        a = np.arange(18).reshape(2, 3, 3)
+        c = np.matmul(a, a, out=a[::-1, ...])
+        assert_(c.base is a.base)
+        assert_equal(c, b)
+
+    def test_diagonal(self):
+        a = np.arange(12).reshape((3, 4))
+        assert_equal(a.diagonal(), [0, 5, 10])
+        assert_equal(a.diagonal(0), [0, 5, 10])
+        assert_equal(a.diagonal(1), [1, 6, 11])
+        assert_equal(a.diagonal(-1), [4, 9])
+        assert_raises(np.AxisError, a.diagonal, axis1=0, axis2=5)
+        assert_raises(np.AxisError, a.diagonal, axis1=5, axis2=0)
+        assert_raises(np.AxisError, a.diagonal, axis1=5, axis2=5)
+        assert_raises(ValueError, a.diagonal, axis1=1, axis2=1)
+
+        b = np.arange(8).reshape((2, 2, 2))
+        assert_equal(b.diagonal(), [[0, 6], [1, 7]])
+        assert_equal(b.diagonal(0), [[0, 6], [1, 7]])
+        assert_equal(b.diagonal(1), [[2], [3]])
+        assert_equal(b.diagonal(-1), [[4], [5]])
+        assert_raises(ValueError, b.diagonal, axis1=0, axis2=0)
+        assert_equal(b.diagonal(0, 1, 2), [[0, 3], [4, 7]])
+        assert_equal(b.diagonal(0, 0, 1), [[0, 6], [1, 7]])
+        assert_equal(b.diagonal(offset=1, axis1=0, axis2=2), [[1], [3]])
+        # Order of axis argument doesn't matter:
+        assert_equal(b.diagonal(0, 2, 1), [[0, 3], [4, 7]])
+
+    def test_diagonal_view_notwriteable(self):
+        a = np.eye(3).diagonal()
+        assert_(not a.flags.writeable)
+        assert_(not a.flags.owndata)
+
+        a = np.diagonal(np.eye(3))
+        assert_(not a.flags.writeable)
+        assert_(not a.flags.owndata)
+
+        a = np.diag(np.eye(3))
+        assert_(not a.flags.writeable)
+        assert_(not a.flags.owndata)
+
+    def test_diagonal_memleak(self):
+        # Regression test for a bug that crept in at one point
+        a = np.zeros((100, 100))
+        if HAS_REFCOUNT:
+            assert_(sys.getrefcount(a) < 50)
+        for i in range(100):
+            a.diagonal()
+        if HAS_REFCOUNT:
+            assert_(sys.getrefcount(a) < 50)
+
+    def test_size_zero_memleak(self):
+        # Regression test for issue 9615
+        # Exercises a special-case code path for dot products of length
+        # zero in cblasfuncs (making it is specific to floating dtypes).
+        a = np.array([], dtype=np.float64)
+        x = np.array(2.0)
+        for _ in range(100):
+            np.dot(a, a, out=x)
+        if HAS_REFCOUNT:
+            assert_(sys.getrefcount(x) < 50)
+
+    def test_trace(self):
+        a = np.arange(12).reshape((3, 4))
+        assert_equal(a.trace(), 15)
+        assert_equal(a.trace(0), 15)
+        assert_equal(a.trace(1), 18)
+        assert_equal(a.trace(-1), 13)
+
+        b = np.arange(8).reshape((2, 2, 2))
+        assert_equal(b.trace(), [6, 8])
+        assert_equal(b.trace(0), [6, 8])
+        assert_equal(b.trace(1), [2, 3])
+        assert_equal(b.trace(-1), [4, 5])
+        assert_equal(b.trace(0, 0, 1), [6, 8])
+        assert_equal(b.trace(0, 0, 2), [5, 9])
+        assert_equal(b.trace(0, 1, 2), [3, 11])
+        assert_equal(b.trace(offset=1, axis1=0, axis2=2), [1, 3])
+
+        out = np.array(1)
+        ret = a.trace(out=out)
+        assert ret is out
+
+    def test_trace_subclass(self):
+        # The class would need to overwrite trace to ensure single-element
+        # output also has the right subclass.
+        class MyArray(np.ndarray):
+            pass
+
+        b = np.arange(8).reshape((2, 2, 2)).view(MyArray)
+        t = b.trace()
+        assert_(isinstance(t, MyArray))
+
+    def test_put(self):
+        icodes = np.typecodes['AllInteger']
+        fcodes = np.typecodes['AllFloat']
+        for dt in icodes + fcodes + 'O':
+            tgt = np.array([0, 1, 0, 3, 0, 5], dtype=dt)
+
+            # test 1-d
+            a = np.zeros(6, dtype=dt)
+            a.put([1, 3, 5], [1, 3, 5])
+            assert_equal(a, tgt)
+
+            # test 2-d
+            a = np.zeros((2, 3), dtype=dt)
+            a.put([1, 3, 5], [1, 3, 5])
+            assert_equal(a, tgt.reshape(2, 3))
+
+        for dt in '?':
+            tgt = np.array([False, True, False, True, False, True], dtype=dt)
+
+            # test 1-d
+            a = np.zeros(6, dtype=dt)
+            a.put([1, 3, 5], [True]*3)
+            assert_equal(a, tgt)
+
+            # test 2-d
+            a = np.zeros((2, 3), dtype=dt)
+            a.put([1, 3, 5], [True]*3)
+            assert_equal(a, tgt.reshape(2, 3))
+
+        # check must be writeable
+        a = np.zeros(6)
+        a.flags.writeable = False
+        assert_raises(ValueError, a.put, [1, 3, 5], [1, 3, 5])
+
+        # when calling np.put, make sure a
+        # TypeError is raised if the object
+        # isn't an ndarray
+        bad_array = [1, 2, 3]
+        assert_raises(TypeError, np.put, bad_array, [0, 2], 5)
+
+    def test_ravel(self):
+        a = np.array([[0, 1], [2, 3]])
+        assert_equal(a.ravel(), [0, 1, 2, 3])
+        assert_(not a.ravel().flags.owndata)
+        assert_equal(a.ravel('F'), [0, 2, 1, 3])
+        assert_equal(a.ravel(order='C'), [0, 1, 2, 3])
+        assert_equal(a.ravel(order='F'), [0, 2, 1, 3])
+        assert_equal(a.ravel(order='A'), [0, 1, 2, 3])
+        assert_(not a.ravel(order='A').flags.owndata)
+        assert_equal(a.ravel(order='K'), [0, 1, 2, 3])
+        assert_(not a.ravel(order='K').flags.owndata)
+        assert_equal(a.ravel(), a.reshape(-1))
+
+        a = np.array([[0, 1], [2, 3]], order='F')
+        assert_equal(a.ravel(), [0, 1, 2, 3])
+        assert_equal(a.ravel(order='A'), [0, 2, 1, 3])
+        assert_equal(a.ravel(order='K'), [0, 2, 1, 3])
+        assert_(not a.ravel(order='A').flags.owndata)
+        assert_(not a.ravel(order='K').flags.owndata)
+        assert_equal(a.ravel(), a.reshape(-1))
+        assert_equal(a.ravel(order='A'), a.reshape(-1, order='A'))
+
+        a = np.array([[0, 1], [2, 3]])[::-1, :]
+        assert_equal(a.ravel(), [2, 3, 0, 1])
+        assert_equal(a.ravel(order='C'), [2, 3, 0, 1])
+        assert_equal(a.ravel(order='F'), [2, 0, 3, 1])
+        assert_equal(a.ravel(order='A'), [2, 3, 0, 1])
+        # 'K' doesn't reverse the axes of negative strides
+        assert_equal(a.ravel(order='K'), [2, 3, 0, 1])
+        assert_(a.ravel(order='K').flags.owndata)
+
+        # Test simple 1-d copy behaviour:
+        a = np.arange(10)[::2]
+        assert_(a.ravel('K').flags.owndata)
+        assert_(a.ravel('C').flags.owndata)
+        assert_(a.ravel('F').flags.owndata)
+
+        # Not contiguous and 1-sized axis with non matching stride
+        a = np.arange(2**3 * 2)[::2]
+        a = a.reshape(2, 1, 2, 2).swapaxes(-1, -2)
+        strides = list(a.strides)
+        strides[1] = 123
+        a.strides = strides
+        assert_(a.ravel(order='K').flags.owndata)
+        assert_equal(a.ravel('K'), np.arange(0, 15, 2))
+
+        # contiguous and 1-sized axis with non matching stride works:
+        a = np.arange(2**3)
+        a = a.reshape(2, 1, 2, 2).swapaxes(-1, -2)
+        strides = list(a.strides)
+        strides[1] = 123
+        a.strides = strides
+        assert_(np.may_share_memory(a.ravel(order='K'), a))
+        assert_equal(a.ravel(order='K'), np.arange(2**3))
+
+        # Test negative strides (not very interesting since non-contiguous):
+        a = np.arange(4)[::-1].reshape(2, 2)
+        assert_(a.ravel(order='C').flags.owndata)
+        assert_(a.ravel(order='K').flags.owndata)
+        assert_equal(a.ravel('C'), [3, 2, 1, 0])
+        assert_equal(a.ravel('K'), [3, 2, 1, 0])
+
+        # 1-element tidy strides test:
+        a = np.array([[1]])
+        a.strides = (123, 432)
+        # If the following stride is not 8, NPY_RELAXED_STRIDES_DEBUG is
+        # messing them up on purpose:
+        if np.ones(1).strides == (8,):
+            assert_(np.may_share_memory(a.ravel('K'), a))
+            assert_equal(a.ravel('K').strides, (a.dtype.itemsize,))
+
+        for order in ('C', 'F', 'A', 'K'):
+            # 0-d corner case:
+            a = np.array(0)
+            assert_equal(a.ravel(order), [0])
+            assert_(np.may_share_memory(a.ravel(order), a))
+
+        # Test that certain non-inplace ravels work right (mostly) for 'K':
+        b = np.arange(2**4 * 2)[::2].reshape(2, 2, 2, 2)
+        a = b[..., ::2]
+        assert_equal(a.ravel('K'), [0, 4, 8, 12, 16, 20, 24, 28])
+        assert_equal(a.ravel('C'), [0, 4, 8, 12, 16, 20, 24, 28])
+        assert_equal(a.ravel('A'), [0, 4, 8, 12, 16, 20, 24, 28])
+        assert_equal(a.ravel('F'), [0, 16, 8, 24, 4, 20, 12, 28])
+
+        a = b[::2, ...]
+        assert_equal(a.ravel('K'), [0, 2, 4, 6, 8, 10, 12, 14])
+        assert_equal(a.ravel('C'), [0, 2, 4, 6, 8, 10, 12, 14])
+        assert_equal(a.ravel('A'), [0, 2, 4, 6, 8, 10, 12, 14])
+        assert_equal(a.ravel('F'), [0, 8, 4, 12, 2, 10, 6, 14])
+
+    def test_ravel_subclass(self):
+        class ArraySubclass(np.ndarray):
+            pass
+
+        a = np.arange(10).view(ArraySubclass)
+        assert_(isinstance(a.ravel('C'), ArraySubclass))
+        assert_(isinstance(a.ravel('F'), ArraySubclass))
+        assert_(isinstance(a.ravel('A'), ArraySubclass))
+        assert_(isinstance(a.ravel('K'), ArraySubclass))
+
+        a = np.arange(10)[::2].view(ArraySubclass)
+        assert_(isinstance(a.ravel('C'), ArraySubclass))
+        assert_(isinstance(a.ravel('F'), ArraySubclass))
+        assert_(isinstance(a.ravel('A'), ArraySubclass))
+        assert_(isinstance(a.ravel('K'), ArraySubclass))
+
+    def test_swapaxes(self):
+        a = np.arange(1*2*3*4).reshape(1, 2, 3, 4).copy()
+        idx = np.indices(a.shape)
+        assert_(a.flags['OWNDATA'])
+        b = a.copy()
+        # check exceptions
+        assert_raises(np.AxisError, a.swapaxes, -5, 0)
+        assert_raises(np.AxisError, a.swapaxes, 4, 0)
+        assert_raises(np.AxisError, a.swapaxes, 0, -5)
+        assert_raises(np.AxisError, a.swapaxes, 0, 4)
+
+        for i in range(-4, 4):
+            for j in range(-4, 4):
+                for k, src in enumerate((a, b)):
+                    c = src.swapaxes(i, j)
+                    # check shape
+                    shape = list(src.shape)
+                    shape[i] = src.shape[j]
+                    shape[j] = src.shape[i]
+                    assert_equal(c.shape, shape, str((i, j, k)))
+                    # check array contents
+                    i0, i1, i2, i3 = [dim-1 for dim in c.shape]
+                    j0, j1, j2, j3 = [dim-1 for dim in src.shape]
+                    assert_equal(src[idx[j0], idx[j1], idx[j2], idx[j3]],
+                                 c[idx[i0], idx[i1], idx[i2], idx[i3]],
+                                 str((i, j, k)))
+                    # check a view is always returned, gh-5260
+                    assert_(not c.flags['OWNDATA'], str((i, j, k)))
+                    # check on non-contiguous input array
+                    if k == 1:
+                        b = c
+
+    def test_conjugate(self):
+        a = np.array([1-1j, 1+1j, 23+23.0j])
+        ac = a.conj()
+        assert_equal(a.real, ac.real)
+        assert_equal(a.imag, -ac.imag)
+        assert_equal(ac, a.conjugate())
+        assert_equal(ac, np.conjugate(a))
+
+        a = np.array([1-1j, 1+1j, 23+23.0j], 'F')
+        ac = a.conj()
+        assert_equal(a.real, ac.real)
+        assert_equal(a.imag, -ac.imag)
+        assert_equal(ac, a.conjugate())
+        assert_equal(ac, np.conjugate(a))
+
+        a = np.array([1, 2, 3])
+        ac = a.conj()
+        assert_equal(a, ac)
+        assert_equal(ac, a.conjugate())
+        assert_equal(ac, np.conjugate(a))
+
+        a = np.array([1.0, 2.0, 3.0])
+        ac = a.conj()
+        assert_equal(a, ac)
+        assert_equal(ac, a.conjugate())
+        assert_equal(ac, np.conjugate(a))
+
+        a = np.array([1-1j, 1+1j, 1, 2.0], object)
+        ac = a.conj()
+        assert_equal(ac, [k.conjugate() for k in a])
+        assert_equal(ac, a.conjugate())
+        assert_equal(ac, np.conjugate(a))
+
+        a = np.array([1-1j, 1, 2.0, 'f'], object)
+        assert_raises(TypeError, lambda: a.conj())
+        assert_raises(TypeError, lambda: a.conjugate())
+
+    def test_conjugate_out(self):
+        # Minimal test for the out argument being passed on correctly
+        # NOTE: The ability to pass `out` is currently undocumented!
+        a = np.array([1-1j, 1+1j, 23+23.0j])
+        out = np.empty_like(a)
+        res = a.conjugate(out)
+        assert res is out
+        assert_array_equal(out, a.conjugate())
+
+    def test__complex__(self):
+        dtypes = ['i1', 'i2', 'i4', 'i8',
+                  'u1', 'u2', 'u4', 'u8',
+                  'f', 'd', 'g', 'F', 'D', 'G',
+                  '?', 'O']
+        for dt in dtypes:
+            a = np.array(7, dtype=dt)
+            b = np.array([7], dtype=dt)
+            c = np.array([[[[[7]]]]], dtype=dt)
+
+            msg = 'dtype: {0}'.format(dt)
+            ap = complex(a)
+            assert_equal(ap, a, msg)
+
+            with assert_warns(DeprecationWarning):
+                bp = complex(b)
+            assert_equal(bp, b, msg)
+
+            with assert_warns(DeprecationWarning):
+                cp = complex(c)
+            assert_equal(cp, c, msg)
+
+    def test__complex__should_not_work(self):
+        dtypes = ['i1', 'i2', 'i4', 'i8',
+                  'u1', 'u2', 'u4', 'u8',
+                  'f', 'd', 'g', 'F', 'D', 'G',
+                  '?', 'O']
+        for dt in dtypes:
+            a = np.array([1, 2, 3], dtype=dt)
+            assert_raises(TypeError, complex, a)
+
+        dt = np.dtype([('a', 'f8'), ('b', 'i1')])
+        b = np.array((1.0, 3), dtype=dt)
+        assert_raises(TypeError, complex, b)
+
+        c = np.array([(1.0, 3), (2e-3, 7)], dtype=dt)
+        assert_raises(TypeError, complex, c)
+
+        d = np.array('1+1j')
+        assert_raises(TypeError, complex, d)
+
+        e = np.array(['1+1j'], 'U')
+        with assert_warns(DeprecationWarning):
+            assert_raises(TypeError, complex, e)
+
+class TestCequenceMethods:
+    def test_array_contains(self):
+        assert_(4.0 in np.arange(16.).reshape(4,4))
+        assert_(20.0 not in np.arange(16.).reshape(4,4))
+
+class TestBinop:
+    def test_inplace(self):
+        # test refcount 1 inplace conversion
+        assert_array_almost_equal(np.array([0.5]) * np.array([1.0, 2.0]),
+                                  [0.5, 1.0])
+
+        d = np.array([0.5, 0.5])[::2]
+        assert_array_almost_equal(d * (d * np.array([1.0, 2.0])),
+                                  [0.25, 0.5])
+
+        a = np.array([0.5])
+        b = np.array([0.5])
+        c = a + b
+        c = a - b
+        c = a * b
+        c = a / b
+        assert_equal(a, b)
+        assert_almost_equal(c, 1.)
+
+        c = a + b * 2. / b * a - a / b
+        assert_equal(a, b)
+        assert_equal(c, 0.5)
+
+        # true divide
+        a = np.array([5])
+        b = np.array([3])
+        c = (a * a) / b
+
+        assert_almost_equal(c, 25 / 3)
+        assert_equal(a, 5)
+        assert_equal(b, 3)
+
+    # ndarray.__rop__ always calls ufunc
+    # ndarray.__iop__ always calls ufunc
+    # ndarray.__op__, __rop__:
+    #   - defer if other has __array_ufunc__ and it is None
+    #           or other is not a subclass and has higher array priority
+    #   - else, call ufunc
+    @pytest.mark.xfail(IS_PYPY, reason="Bug in pypy3.{9, 10}-v7.3.13, #24862")
+    def test_ufunc_binop_interaction(self):
+        # Python method name (without underscores)
+        #   -> (numpy ufunc, has_in_place_version, preferred_dtype)
+        ops = {
+            'add':      (np.add, True, float),
+            'sub':      (np.subtract, True, float),
+            'mul':      (np.multiply, True, float),
+            'truediv':  (np.true_divide, True, float),
+            'floordiv': (np.floor_divide, True, float),
+            'mod':      (np.remainder, True, float),
+            'divmod':   (np.divmod, False, float),
+            'pow':      (np.power, True, int),
+            'lshift':   (np.left_shift, True, int),
+            'rshift':   (np.right_shift, True, int),
+            'and':      (np.bitwise_and, True, int),
+            'xor':      (np.bitwise_xor, True, int),
+            'or':       (np.bitwise_or, True, int),
+            'matmul':   (np.matmul, True, float),
+            # 'ge':       (np.less_equal, False),
+            # 'gt':       (np.less, False),
+            # 'le':       (np.greater_equal, False),
+            # 'lt':       (np.greater, False),
+            # 'eq':       (np.equal, False),
+            # 'ne':       (np.not_equal, False),
+        }
+
+        class Coerced(Exception):
+            pass
+
+        def array_impl(self):
+            raise Coerced
+
+        def op_impl(self, other):
+            return "forward"
+
+        def rop_impl(self, other):
+            return "reverse"
+
+        def iop_impl(self, other):
+            return "in-place"
+
+        def array_ufunc_impl(self, ufunc, method, *args, **kwargs):
+            return ("__array_ufunc__", ufunc, method, args, kwargs)
+
+        # Create an object with the given base, in the given module, with a
+        # bunch of placeholder __op__ methods, and optionally a
+        # __array_ufunc__ and __array_priority__.
+        def make_obj(base, array_priority=False, array_ufunc=False,
+                     alleged_module="__main__"):
+            class_namespace = {"__array__": array_impl}
+            if array_priority is not False:
+                class_namespace["__array_priority__"] = array_priority
+            for op in ops:
+                class_namespace["__{0}__".format(op)] = op_impl
+                class_namespace["__r{0}__".format(op)] = rop_impl
+                class_namespace["__i{0}__".format(op)] = iop_impl
+            if array_ufunc is not False:
+                class_namespace["__array_ufunc__"] = array_ufunc
+            eval_namespace = {"base": base,
+                              "class_namespace": class_namespace,
+                              "__name__": alleged_module,
+                              }
+            MyType = eval("type('MyType', (base,), class_namespace)",
+                          eval_namespace)
+            if issubclass(MyType, np.ndarray):
+                # Use this range to avoid special case weirdnesses around
+                # divide-by-0, pow(x, 2), overflow due to pow(big, big), etc.
+                return np.arange(3, 7).reshape(2, 2).view(MyType)
+            else:
+                return MyType()
+
+        def check(obj, binop_override_expected, ufunc_override_expected,
+                  inplace_override_expected, check_scalar=True):
+            for op, (ufunc, has_inplace, dtype) in ops.items():
+                err_msg = ('op: %s, ufunc: %s, has_inplace: %s, dtype: %s'
+                           % (op, ufunc, has_inplace, dtype))
+                check_objs = [np.arange(3, 7, dtype=dtype).reshape(2, 2)]
+                if check_scalar:
+                    check_objs.append(check_objs[0][0])
+                for arr in check_objs:
+                    arr_method = getattr(arr, "__{0}__".format(op))
+
+                    def first_out_arg(result):
+                        if op == "divmod":
+                            assert_(isinstance(result, tuple))
+                            return result[0]
+                        else:
+                            return result
+
+                    # arr __op__ obj
+                    if binop_override_expected:
+                        assert_equal(arr_method(obj), NotImplemented, err_msg)
+                    elif ufunc_override_expected:
+                        assert_equal(arr_method(obj)[0], "__array_ufunc__",
+                                     err_msg)
+                    else:
+                        if (isinstance(obj, np.ndarray) and
+                            (type(obj).__array_ufunc__ is
+                             np.ndarray.__array_ufunc__)):
+                            # __array__ gets ignored
+                            res = first_out_arg(arr_method(obj))
+                            assert_(res.__class__ is obj.__class__, err_msg)
+                        else:
+                            assert_raises((TypeError, Coerced),
+                                          arr_method, obj, err_msg=err_msg)
+                    # obj __op__ arr
+                    arr_rmethod = getattr(arr, "__r{0}__".format(op))
+                    if ufunc_override_expected:
+                        res = arr_rmethod(obj)
+                        assert_equal(res[0], "__array_ufunc__",
+                                     err_msg=err_msg)
+                        assert_equal(res[1], ufunc, err_msg=err_msg)
+                    else:
+                        if (isinstance(obj, np.ndarray) and
+                                (type(obj).__array_ufunc__ is
+                                 np.ndarray.__array_ufunc__)):
+                            # __array__ gets ignored
+                            res = first_out_arg(arr_rmethod(obj))
+                            assert_(res.__class__ is obj.__class__, err_msg)
+                        else:
+                            # __array_ufunc__ = "asdf" creates a TypeError
+                            assert_raises((TypeError, Coerced),
+                                          arr_rmethod, obj, err_msg=err_msg)
+
+                    # arr __iop__ obj
+                    # array scalars don't have in-place operators
+                    if has_inplace and isinstance(arr, np.ndarray):
+                        arr_imethod = getattr(arr, "__i{0}__".format(op))
+                        if inplace_override_expected:
+                            assert_equal(arr_method(obj), NotImplemented,
+                                         err_msg=err_msg)
+                        elif ufunc_override_expected:
+                            res = arr_imethod(obj)
+                            assert_equal(res[0], "__array_ufunc__", err_msg)
+                            assert_equal(res[1], ufunc, err_msg)
+                            assert_(type(res[-1]["out"]) is tuple, err_msg)
+                            assert_(res[-1]["out"][0] is arr, err_msg)
+                        else:
+                            if (isinstance(obj, np.ndarray) and
+                                    (type(obj).__array_ufunc__ is
+                                    np.ndarray.__array_ufunc__)):
+                                # __array__ gets ignored
+                                assert_(arr_imethod(obj) is arr, err_msg)
+                            else:
+                                assert_raises((TypeError, Coerced),
+                                              arr_imethod, obj,
+                                              err_msg=err_msg)
+
+                    op_fn = getattr(operator, op, None)
+                    if op_fn is None:
+                        op_fn = getattr(operator, op + "_", None)
+                    if op_fn is None:
+                        op_fn = getattr(builtins, op)
+                    assert_equal(op_fn(obj, arr), "forward", err_msg)
+                    if not isinstance(obj, np.ndarray):
+                        if binop_override_expected:
+                            assert_equal(op_fn(arr, obj), "reverse", err_msg)
+                        elif ufunc_override_expected:
+                            assert_equal(op_fn(arr, obj)[0], "__array_ufunc__",
+                                         err_msg)
+                    if ufunc_override_expected:
+                        assert_equal(ufunc(obj, arr)[0], "__array_ufunc__",
+                                     err_msg)
+
+        # No array priority, no array_ufunc -> nothing called
+        check(make_obj(object), False, False, False)
+        # Negative array priority, no array_ufunc -> nothing called
+        # (has to be very negative, because scalar priority is -1000000.0)
+        check(make_obj(object, array_priority=-2**30), False, False, False)
+        # Positive array priority, no array_ufunc -> binops and iops only
+        check(make_obj(object, array_priority=1), True, False, True)
+        # ndarray ignores array_priority for ndarray subclasses
+        check(make_obj(np.ndarray, array_priority=1), False, False, False,
+              check_scalar=False)
+        # Positive array_priority and array_ufunc -> array_ufunc only
+        check(make_obj(object, array_priority=1,
+                       array_ufunc=array_ufunc_impl), False, True, False)
+        check(make_obj(np.ndarray, array_priority=1,
+                       array_ufunc=array_ufunc_impl), False, True, False)
+        # array_ufunc set to None -> defer binops only
+        check(make_obj(object, array_ufunc=None), True, False, False)
+        check(make_obj(np.ndarray, array_ufunc=None), True, False, False,
+              check_scalar=False)
+
+    @pytest.mark.parametrize("priority", [None, "runtime error"])
+    def test_ufunc_binop_bad_array_priority(self, priority):
+        # Mainly checks that this does not crash.  The second array has a lower
+        # priority than -1 ("error value").  If the __radd__ actually exists,
+        # bad things can happen (I think via the scalar paths).
+        # In principle both of these can probably just be errors in the future.
+        class BadPriority:
+            @property
+            def __array_priority__(self):
+                if priority == "runtime error":
+                    raise RuntimeError("RuntimeError in __array_priority__!")
+                return priority
+
+            def __radd__(self, other):
+                return "result"
+
+        class LowPriority(np.ndarray):
+            __array_priority__ = -1000
+
+        # Priority failure uses the same as scalars (smaller -1000).  So the
+        # LowPriority wins with 'result' for each element (inner operation).
+        res = np.arange(3).view(LowPriority) + BadPriority()
+        assert res.shape == (3,)
+        assert res[0] == 'result'
+
+
+    def test_ufunc_override_normalize_signature(self):
+        # gh-5674
+        class SomeClass:
+            def __array_ufunc__(self, ufunc, method, *inputs, **kw):
+                return kw
+
+        a = SomeClass()
+        kw = np.add(a, [1])
+        assert_('sig' not in kw and 'signature' not in kw)
+        kw = np.add(a, [1], sig='ii->i')
+        assert_('sig' not in kw and 'signature' in kw)
+        assert_equal(kw['signature'], 'ii->i')
+        kw = np.add(a, [1], signature='ii->i')
+        assert_('sig' not in kw and 'signature' in kw)
+        assert_equal(kw['signature'], 'ii->i')
+
+    def test_array_ufunc_index(self):
+        # Check that index is set appropriately, also if only an output
+        # is passed on (latter is another regression tests for github bug 4753)
+        # This also checks implicitly that 'out' is always a tuple.
+        class CheckIndex:
+            def __array_ufunc__(self, ufunc, method, *inputs, **kw):
+                for i, a in enumerate(inputs):
+                    if a is self:
+                        return i
+                # calls below mean we must be in an output.
+                for j, a in enumerate(kw['out']):
+                    if a is self:
+                        return (j,)
+
+        a = CheckIndex()
+        dummy = np.arange(2.)
+        # 1 input, 1 output
+        assert_equal(np.sin(a), 0)
+        assert_equal(np.sin(dummy, a), (0,))
+        assert_equal(np.sin(dummy, out=a), (0,))
+        assert_equal(np.sin(dummy, out=(a,)), (0,))
+        assert_equal(np.sin(a, a), 0)
+        assert_equal(np.sin(a, out=a), 0)
+        assert_equal(np.sin(a, out=(a,)), 0)
+        # 1 input, 2 outputs
+        assert_equal(np.modf(dummy, a), (0,))
+        assert_equal(np.modf(dummy, None, a), (1,))
+        assert_equal(np.modf(dummy, dummy, a), (1,))
+        assert_equal(np.modf(dummy, out=(a, None)), (0,))
+        assert_equal(np.modf(dummy, out=(a, dummy)), (0,))
+        assert_equal(np.modf(dummy, out=(None, a)), (1,))
+        assert_equal(np.modf(dummy, out=(dummy, a)), (1,))
+        assert_equal(np.modf(a, out=(dummy, a)), 0)
+        with assert_raises(TypeError):
+            # Out argument must be tuple, since there are multiple outputs
+            np.modf(dummy, out=a)
+
+        assert_raises(ValueError, np.modf, dummy, out=(a,))
+
+        # 2 inputs, 1 output
+        assert_equal(np.add(a, dummy), 0)
+        assert_equal(np.add(dummy, a), 1)
+        assert_equal(np.add(dummy, dummy, a), (0,))
+        assert_equal(np.add(dummy, a, a), 1)
+        assert_equal(np.add(dummy, dummy, out=a), (0,))
+        assert_equal(np.add(dummy, dummy, out=(a,)), (0,))
+        assert_equal(np.add(a, dummy, out=a), 0)
+
+    def test_out_override(self):
+        # regression test for github bug 4753
+        class OutClass(np.ndarray):
+            def __array_ufunc__(self, ufunc, method, *inputs, **kw):
+                if 'out' in kw:
+                    tmp_kw = kw.copy()
+                    tmp_kw.pop('out')
+                    func = getattr(ufunc, method)
+                    kw['out'][0][...] = func(*inputs, **tmp_kw)
+
+        A = np.array([0]).view(OutClass)
+        B = np.array([5])
+        C = np.array([6])
+        np.multiply(C, B, A)
+        assert_equal(A[0], 30)
+        assert_(isinstance(A, OutClass))
+        A[0] = 0
+        np.multiply(C, B, out=A)
+        assert_equal(A[0], 30)
+        assert_(isinstance(A, OutClass))
+
+    def test_pow_override_with_errors(self):
+        # regression test for gh-9112
+        class PowerOnly(np.ndarray):
+            def __array_ufunc__(self, ufunc, method, *inputs, **kw):
+                if ufunc is not np.power:
+                    raise NotImplementedError
+                return "POWER!"
+        # explicit cast to float, to ensure the fast power path is taken.
+        a = np.array(5., dtype=np.float64).view(PowerOnly)
+        assert_equal(a ** 2.5, "POWER!")
+        with assert_raises(NotImplementedError):
+            a ** 0.5
+        with assert_raises(NotImplementedError):
+            a ** 0
+        with assert_raises(NotImplementedError):
+            a ** 1
+        with assert_raises(NotImplementedError):
+            a ** -1
+        with assert_raises(NotImplementedError):
+            a ** 2
+
+    def test_pow_array_object_dtype(self):
+        # test pow on arrays of object dtype
+        class SomeClass:
+            def __init__(self, num=None):
+                self.num = num
+
+            # want to ensure a fast pow path is not taken
+            def __mul__(self, other):
+                raise AssertionError('__mul__ should not be called')
+
+            def __div__(self, other):
+                raise AssertionError('__div__ should not be called')
+
+            def __pow__(self, exp):
+                return SomeClass(num=self.num ** exp)
+
+            def __eq__(self, other):
+                if isinstance(other, SomeClass):
+                    return self.num == other.num
+
+            __rpow__ = __pow__
+
+        def pow_for(exp, arr):
+            return np.array([x ** exp for x in arr])
+
+        obj_arr = np.array([SomeClass(1), SomeClass(2), SomeClass(3)])
+
+        assert_equal(obj_arr ** 0.5, pow_for(0.5, obj_arr))
+        assert_equal(obj_arr ** 0, pow_for(0, obj_arr))
+        assert_equal(obj_arr ** 1, pow_for(1, obj_arr))
+        assert_equal(obj_arr ** -1, pow_for(-1, obj_arr))
+        assert_equal(obj_arr ** 2, pow_for(2, obj_arr))
+
+    def test_pos_array_ufunc_override(self):
+        class A(np.ndarray):
+            def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
+                return getattr(ufunc, method)(*[i.view(np.ndarray) for
+                                                i in inputs], **kwargs)
+        tst = np.array('foo').view(A)
+        with assert_raises(TypeError):
+            +tst
+
+
+class TestTemporaryElide:
+    # elision is only triggered on relatively large arrays
+
+    def test_extension_incref_elide(self):
+        # test extension (e.g. cython) calling PyNumber_* slots without
+        # increasing the reference counts
+        #
+        # def incref_elide(a):
+        #    d = input.copy() # refcount 1
+        #    return d, d + d # PyNumber_Add without increasing refcount
+        from numpy.core._multiarray_tests import incref_elide
+        d = np.ones(100000)
+        orig, res = incref_elide(d)
+        d + d
+        # the return original should not be changed to an inplace operation
+        assert_array_equal(orig, d)
+        assert_array_equal(res, d + d)
+
+    def test_extension_incref_elide_stack(self):
+        # scanning if the refcount == 1 object is on the python stack to check
+        # that we are called directly from python is flawed as object may still
+        # be above the stack pointer and we have no access to the top of it
+        #
+        # def incref_elide_l(d):
+        #    return l[4] + l[4] # PyNumber_Add without increasing refcount
+        from numpy.core._multiarray_tests import incref_elide_l
+        # padding with 1 makes sure the object on the stack is not overwritten
+        l = [1, 1, 1, 1, np.ones(100000)]
+        res = incref_elide_l(l)
+        # the return original should not be changed to an inplace operation
+        assert_array_equal(l[4], np.ones(100000))
+        assert_array_equal(res, l[4] + l[4])
+
+    def test_temporary_with_cast(self):
+        # check that we don't elide into a temporary which would need casting
+        d = np.ones(200000, dtype=np.int64)
+        assert_equal(((d + d) + 2**222).dtype, np.dtype('O'))
+
+        r = ((d + d) / 2)
+        assert_equal(r.dtype, np.dtype('f8'))
+
+        r = np.true_divide((d + d), 2)
+        assert_equal(r.dtype, np.dtype('f8'))
+
+        r = ((d + d) / 2.)
+        assert_equal(r.dtype, np.dtype('f8'))
+
+        r = ((d + d) // 2)
+        assert_equal(r.dtype, np.dtype(np.int64))
+
+        # commutative elision into the astype result
+        f = np.ones(100000, dtype=np.float32)
+        assert_equal(((f + f) + f.astype(np.float64)).dtype, np.dtype('f8'))
+
+        # no elision into lower type
+        d = f.astype(np.float64)
+        assert_equal(((f + f) + d).dtype, d.dtype)
+        l = np.ones(100000, dtype=np.longdouble)
+        assert_equal(((d + d) + l).dtype, l.dtype)
+
+        # test unary abs with different output dtype
+        for dt in (np.complex64, np.complex128, np.clongdouble):
+            c = np.ones(100000, dtype=dt)
+            r = abs(c * 2.0)
+            assert_equal(r.dtype, np.dtype('f%d' % (c.itemsize // 2)))
+
+    def test_elide_broadcast(self):
+        # test no elision on broadcast to higher dimension
+        # only triggers elision code path in debug mode as triggering it in
+        # normal mode needs 256kb large matching dimension, so a lot of memory
+        d = np.ones((2000, 1), dtype=int)
+        b = np.ones((2000), dtype=bool)
+        r = (1 - d) + b
+        assert_equal(r, 1)
+        assert_equal(r.shape, (2000, 2000))
+
+    def test_elide_scalar(self):
+        # check inplace op does not create ndarray from scalars
+        a = np.bool_()
+        assert_(type(~(a & a)) is np.bool_)
+
+    def test_elide_scalar_readonly(self):
+        # The imaginary part of a real array is readonly. This needs to go
+        # through fast_scalar_power which is only called for powers of
+        # +1, -1, 0, 0.5, and 2, so use 2. Also need valid refcount for
+        # elision which can be gotten for the imaginary part of a real
+        # array. Should not error.
+        a = np.empty(100000, dtype=np.float64)
+        a.imag ** 2
+
+    def test_elide_readonly(self):
+        # don't try to elide readonly temporaries
+        r = np.asarray(np.broadcast_to(np.zeros(1), 100000).flat) * 0.0
+        assert_equal(r, 0)
+
+    def test_elide_updateifcopy(self):
+        a = np.ones(2**20)[::2]
+        b = a.flat.__array__() + 1
+        del b
+        assert_equal(a, 1)
+
+
+class TestCAPI:
+    def test_IsPythonScalar(self):
+        from numpy.core._multiarray_tests import IsPythonScalar
+        assert_(IsPythonScalar(b'foobar'))
+        assert_(IsPythonScalar(1))
+        assert_(IsPythonScalar(2**80))
+        assert_(IsPythonScalar(2.))
+        assert_(IsPythonScalar("a"))
+
+    @pytest.mark.parametrize("converter",
+             [_multiarray_tests.run_scalar_intp_converter,
+              _multiarray_tests.run_scalar_intp_from_sequence])
+    def test_intp_sequence_converters(self, converter):
+        # Test simple values (-1 is special for error return paths)
+        assert converter(10) == (10,)
+        assert converter(-1) == (-1,)
+        # A 0-D array looks a bit like a sequence but must take the integer
+        # path:
+        assert converter(np.array(123)) == (123,)
+        # Test simple sequences (intp_from_sequence only supports length 1):
+        assert converter((10,)) == (10,)
+        assert converter(np.array([11])) == (11,)
+
+    @pytest.mark.parametrize("converter",
+             [_multiarray_tests.run_scalar_intp_converter,
+              _multiarray_tests.run_scalar_intp_from_sequence])
+    @pytest.mark.skipif(IS_PYPY and sys.implementation.version <= (7, 3, 8),
+            reason="PyPy bug in error formatting")
+    def test_intp_sequence_converters_errors(self, converter):
+        with pytest.raises(TypeError,
+                match="expected a sequence of integers or a single integer, "):
+            converter(object())
+        with pytest.raises(TypeError,
+                match="expected a sequence of integers or a single integer, "
+                      "got '32.0'"):
+            converter(32.)
+        with pytest.raises(TypeError,
+                match="'float' object cannot be interpreted as an integer"):
+            converter([32.])
+        with pytest.raises(ValueError,
+                match="Maximum allowed dimension"):
+            # These converters currently convert overflows to a ValueError
+            converter(2**64)
+
+
+class TestSubscripting:
+    def test_test_zero_rank(self):
+        x = np.array([1, 2, 3])
+        assert_(isinstance(x[0], np.int_))
+        assert_(type(x[0, ...]) is np.ndarray)
+
+
+class TestPickling:
+    @pytest.mark.skipif(pickle.HIGHEST_PROTOCOL >= 5,
+                        reason=('this tests the error messages when trying to'
+                                'protocol 5 although it is not available'))
+    def test_correct_protocol5_error_message(self):
+        array = np.arange(10)
+
+    def test_record_array_with_object_dtype(self):
+        my_object = object()
+
+        arr_with_object = np.array(
+                [(my_object, 1, 2.0)],
+                dtype=[('a', object), ('b', int), ('c', float)])
+        arr_without_object = np.array(
+                [('xxx', 1, 2.0)],
+                dtype=[('a', str), ('b', int), ('c', float)])
+
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            depickled_arr_with_object = pickle.loads(
+                    pickle.dumps(arr_with_object, protocol=proto))
+            depickled_arr_without_object = pickle.loads(
+                    pickle.dumps(arr_without_object, protocol=proto))
+
+            assert_equal(arr_with_object.dtype,
+                         depickled_arr_with_object.dtype)
+            assert_equal(arr_without_object.dtype,
+                         depickled_arr_without_object.dtype)
+
+    @pytest.mark.skipif(pickle.HIGHEST_PROTOCOL < 5,
+                        reason="requires pickle protocol 5")
+    def test_f_contiguous_array(self):
+        f_contiguous_array = np.array([[1, 2, 3], [4, 5, 6]], order='F')
+        buffers = []
+
+        # When using pickle protocol 5, Fortran-contiguous arrays can be
+        # serialized using out-of-band buffers
+        bytes_string = pickle.dumps(f_contiguous_array, protocol=5,
+                                    buffer_callback=buffers.append)
+
+        assert len(buffers) > 0
+
+        depickled_f_contiguous_array = pickle.loads(bytes_string,
+                                                    buffers=buffers)
+
+        assert_equal(f_contiguous_array, depickled_f_contiguous_array)
+
+    def test_non_contiguous_array(self):
+        non_contiguous_array = np.arange(12).reshape(3, 4)[:, :2]
+        assert not non_contiguous_array.flags.c_contiguous
+        assert not non_contiguous_array.flags.f_contiguous
+
+        # make sure non-contiguous arrays can be pickled-depickled
+        # using any protocol
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            depickled_non_contiguous_array = pickle.loads(
+                    pickle.dumps(non_contiguous_array, protocol=proto))
+
+            assert_equal(non_contiguous_array, depickled_non_contiguous_array)
+
+    def test_roundtrip(self):
+        for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
+            carray = np.array([[2, 9], [7, 0], [3, 8]])
+            DATA = [
+                carray,
+                np.transpose(carray),
+                np.array([('xxx', 1, 2.0)], dtype=[('a', (str, 3)), ('b', int),
+                                                   ('c', float)])
+            ]
+
+            refs = [weakref.ref(a) for a in DATA]
+            for a in DATA:
+                assert_equal(
+                        a, pickle.loads(pickle.dumps(a, protocol=proto)),
+                        err_msg="%r" % a)
+            del a, DATA, carray
+            break_cycles()
+            # check for reference leaks (gh-12793)
+            for ref in refs:
+                assert ref() is None
+
+    def _loads(self, obj):
+        return pickle.loads(obj, encoding='latin1')
+
+    # version 0 pickles, using protocol=2 to pickle
+    # version 0 doesn't have a version field
+    def test_version0_int8(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x04\x85cnumpy\ndtype\nq\x04U\x02i1K\x00K\x01\x87Rq\x05(U\x01|NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89U\x04\x01\x02\x03\x04tb.'
+        a = np.array([1, 2, 3, 4], dtype=np.int8)
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_version0_float32(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x04\x85cnumpy\ndtype\nq\x04U\x02f4K\x00K\x01\x87Rq\x05(U\x01<NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89U\x10\x00\x00\x80?\x00\x00\x00@\x00\x00@@\x00\x00\x80@tb.'
+        a = np.array([1.0, 2.0, 3.0, 4.0], dtype=np.float32)
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_version0_object(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x02\x85cnumpy\ndtype\nq\x04U\x02O8K\x00K\x01\x87Rq\x05(U\x01|NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89]q\x06(}q\x07U\x01aK\x01s}q\x08U\x01bK\x02setb.'
+        a = np.array([{'a': 1}, {'b': 2}])
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    # version 1 pickles, using protocol=2 to pickle
+    def test_version1_int8(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x01K\x04\x85cnumpy\ndtype\nq\x04U\x02i1K\x00K\x01\x87Rq\x05(K\x01U\x01|NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89U\x04\x01\x02\x03\x04tb.'
+        a = np.array([1, 2, 3, 4], dtype=np.int8)
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_version1_float32(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x01K\x04\x85cnumpy\ndtype\nq\x04U\x02f4K\x00K\x01\x87Rq\x05(K\x01U\x01<NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89U\x10\x00\x00\x80?\x00\x00\x00@\x00\x00@@\x00\x00\x80@tb.'
+        a = np.array([1.0, 2.0, 3.0, 4.0], dtype=np.float32)
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_version1_object(self):
+        s = b'\x80\x02cnumpy.core._internal\n_reconstruct\nq\x01cnumpy\nndarray\nq\x02K\x00\x85U\x01b\x87Rq\x03(K\x01K\x02\x85cnumpy\ndtype\nq\x04U\x02O8K\x00K\x01\x87Rq\x05(K\x01U\x01|NNJ\xff\xff\xff\xffJ\xff\xff\xff\xfftb\x89]q\x06(}q\x07U\x01aK\x01s}q\x08U\x01bK\x02setb.'
+        a = np.array([{'a': 1}, {'b': 2}])
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_subarray_int_shape(self):
+        s = b"cnumpy.core.multiarray\n_reconstruct\np0\n(cnumpy\nndarray\np1\n(I0\ntp2\nS'b'\np3\ntp4\nRp5\n(I1\n(I1\ntp6\ncnumpy\ndtype\np7\n(S'V6'\np8\nI0\nI1\ntp9\nRp10\n(I3\nS'|'\np11\nN(S'a'\np12\ng3\ntp13\n(dp14\ng12\n(g7\n(S'V4'\np15\nI0\nI1\ntp16\nRp17\n(I3\nS'|'\np18\n(g7\n(S'i1'\np19\nI0\nI1\ntp20\nRp21\n(I3\nS'|'\np22\nNNNI-1\nI-1\nI0\ntp23\nb(I2\nI2\ntp24\ntp25\nNNI4\nI1\nI0\ntp26\nbI0\ntp27\nsg3\n(g7\n(S'V2'\np28\nI0\nI1\ntp29\nRp30\n(I3\nS'|'\np31\n(g21\nI2\ntp32\nNNI2\nI1\nI0\ntp33\nbI4\ntp34\nsI6\nI1\nI0\ntp35\nbI00\nS'\\x01\\x01\\x01\\x01\\x01\\x02'\np36\ntp37\nb."
+        a = np.array([(1, (1, 2))], dtype=[('a', 'i1', (2, 2)), ('b', 'i1', 2)])
+        p = self._loads(s)
+        assert_equal(a, p)
+
+    def test_datetime64_byteorder(self):
+        original = np.array([['2015-02-24T00:00:00.000000000']], dtype='datetime64[ns]')
+
+        original_byte_reversed = original.copy(order='K')
+        original_byte_reversed.dtype = original_byte_reversed.dtype.newbyteorder('S')
+        original_byte_reversed.byteswap(inplace=True)
+
+        new = pickle.loads(pickle.dumps(original_byte_reversed))
+
+        assert_equal(original.dtype, new.dtype)
+
+
+class TestFancyIndexing:
+    def test_list(self):
+        x = np.ones((1, 1))
+        x[:, [0]] = 2.0
+        assert_array_equal(x, np.array([[2.0]]))
+
+        x = np.ones((1, 1, 1))
+        x[:, :, [0]] = 2.0
+        assert_array_equal(x, np.array([[[2.0]]]))
+
+    def test_tuple(self):
+        x = np.ones((1, 1))
+        x[:, (0,)] = 2.0
+        assert_array_equal(x, np.array([[2.0]]))
+        x = np.ones((1, 1, 1))
+        x[:, :, (0,)] = 2.0
+        assert_array_equal(x, np.array([[[2.0]]]))
+
+    def test_mask(self):
+        x = np.array([1, 2, 3, 4])
+        m = np.array([0, 1, 0, 0], bool)
+        assert_array_equal(x[m], np.array([2]))
+
+    def test_mask2(self):
+        x = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
+        m = np.array([0, 1], bool)
+        m2 = np.array([[0, 1, 0, 0], [1, 0, 0, 0]], bool)
+        m3 = np.array([[0, 1, 0, 0], [0, 0, 0, 0]], bool)
+        assert_array_equal(x[m], np.array([[5, 6, 7, 8]]))
+        assert_array_equal(x[m2], np.array([2, 5]))
+        assert_array_equal(x[m3], np.array([2]))
+
+    def test_assign_mask(self):
+        x = np.array([1, 2, 3, 4])
+        m = np.array([0, 1, 0, 0], bool)
+        x[m] = 5
+        assert_array_equal(x, np.array([1, 5, 3, 4]))
+
+    def test_assign_mask2(self):
+        xorig = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
+        m = np.array([0, 1], bool)
+        m2 = np.array([[0, 1, 0, 0], [1, 0, 0, 0]], bool)
+        m3 = np.array([[0, 1, 0, 0], [0, 0, 0, 0]], bool)
+        x = xorig.copy()
+        x[m] = 10
+        assert_array_equal(x, np.array([[1, 2, 3, 4], [10, 10, 10, 10]]))
+        x = xorig.copy()
+        x[m2] = 10
+        assert_array_equal(x, np.array([[1, 10, 3, 4], [10, 6, 7, 8]]))
+        x = xorig.copy()
+        x[m3] = 10
+        assert_array_equal(x, np.array([[1, 10, 3, 4], [5, 6, 7, 8]]))
+
+
+class TestStringCompare:
+    def test_string(self):
+        g1 = np.array(["This", "is", "example"])
+        g2 = np.array(["This", "was", "example"])
+        assert_array_equal(g1 == g2, [g1[i] == g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 != g2, [g1[i] != g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 <= g2, [g1[i] <= g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 >= g2, [g1[i] >= g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 < g2, [g1[i] < g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 > g2, [g1[i] > g2[i] for i in [0, 1, 2]])
+
+    def test_mixed(self):
+        g1 = np.array(["spam", "spa", "spammer", "and eggs"])
+        g2 = "spam"
+        assert_array_equal(g1 == g2, [x == g2 for x in g1])
+        assert_array_equal(g1 != g2, [x != g2 for x in g1])
+        assert_array_equal(g1 < g2, [x < g2 for x in g1])
+        assert_array_equal(g1 > g2, [x > g2 for x in g1])
+        assert_array_equal(g1 <= g2, [x <= g2 for x in g1])
+        assert_array_equal(g1 >= g2, [x >= g2 for x in g1])
+
+    def test_unicode(self):
+        g1 = np.array(["This", "is", "example"])
+        g2 = np.array(["This", "was", "example"])
+        assert_array_equal(g1 == g2, [g1[i] == g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 != g2, [g1[i] != g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 <= g2, [g1[i] <= g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 >= g2, [g1[i] >= g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 < g2,  [g1[i] < g2[i] for i in [0, 1, 2]])
+        assert_array_equal(g1 > g2,  [g1[i] > g2[i] for i in [0, 1, 2]])
+
+class TestArgmaxArgminCommon:
+
+    sizes = [(), (3,), (3, 2), (2, 3),
+             (3, 3), (2, 3, 4), (4, 3, 2),
+             (1, 2, 3, 4), (2, 3, 4, 1),
+             (3, 4, 1, 2), (4, 1, 2, 3),
+             (64,), (128,), (256,)]
+
+    @pytest.mark.parametrize("size, axis", itertools.chain(*[[(size, axis)
+        for axis in list(range(-len(size), len(size))) + [None]]
+        for size in sizes]))
+    @pytest.mark.parametrize('method', [np.argmax, np.argmin])
+    def test_np_argmin_argmax_keepdims(self, size, axis, method):
+
+        arr = np.random.normal(size=size)
+
+        # contiguous arrays
+        if axis is None:
+            new_shape = [1 for _ in range(len(size))]
+        else:
+            new_shape = list(size)
+            new_shape[axis] = 1
+        new_shape = tuple(new_shape)
+
+        _res_orig = method(arr, axis=axis)
+        res_orig = _res_orig.reshape(new_shape)
+        res = method(arr, axis=axis, keepdims=True)
+        assert_equal(res, res_orig)
+        assert_(res.shape == new_shape)
+        outarray = np.empty(res.shape, dtype=res.dtype)
+        res1 = method(arr, axis=axis, out=outarray,
+                            keepdims=True)
+        assert_(res1 is outarray)
+        assert_equal(res, outarray)
+
+        if len(size) > 0:
+            wrong_shape = list(new_shape)
+            if axis is not None:
+                wrong_shape[axis] = 2
+            else:
+                wrong_shape[0] = 2
+            wrong_outarray = np.empty(wrong_shape, dtype=res.dtype)
+            with pytest.raises(ValueError):
+                method(arr.T, axis=axis,
+                        out=wrong_outarray, keepdims=True)
+
+        # non-contiguous arrays
+        if axis is None:
+            new_shape = [1 for _ in range(len(size))]
+        else:
+            new_shape = list(size)[::-1]
+            new_shape[axis] = 1
+        new_shape = tuple(new_shape)
+
+        _res_orig = method(arr.T, axis=axis)
+        res_orig = _res_orig.reshape(new_shape)
+        res = method(arr.T, axis=axis, keepdims=True)
+        assert_equal(res, res_orig)
+        assert_(res.shape == new_shape)
+        outarray = np.empty(new_shape[::-1], dtype=res.dtype)
+        outarray = outarray.T
+        res1 = method(arr.T, axis=axis, out=outarray,
+                            keepdims=True)
+        assert_(res1 is outarray)
+        assert_equal(res, outarray)
+
+        if len(size) > 0:
+            # one dimension lesser for non-zero sized
+            # array should raise an error
+            with pytest.raises(ValueError):
+                method(arr[0], axis=axis,
+                        out=outarray, keepdims=True)
+
+        if len(size) > 0:
+            wrong_shape = list(new_shape)
+            if axis is not None:
+                wrong_shape[axis] = 2
+            else:
+                wrong_shape[0] = 2
+            wrong_outarray = np.empty(wrong_shape, dtype=res.dtype)
+            with pytest.raises(ValueError):
+                method(arr.T, axis=axis,
+                        out=wrong_outarray, keepdims=True)
+
+    @pytest.mark.parametrize('method', ['max', 'min'])
+    def test_all(self, method):
+        a = np.random.normal(0, 1, (4, 5, 6, 7, 8))
+        arg_method = getattr(a, 'arg' + method)
+        val_method = getattr(a, method)
+        for i in range(a.ndim):
+            a_maxmin = val_method(i)
+            aarg_maxmin = arg_method(i)
+            axes = list(range(a.ndim))
+            axes.remove(i)
+            assert_(np.all(a_maxmin == aarg_maxmin.choose(
+                                        *a.transpose(i, *axes))))
+
+    @pytest.mark.parametrize('method', ['argmax', 'argmin'])
+    def test_output_shape(self, method):
+        # see also gh-616
+        a = np.ones((10, 5))
+        arg_method = getattr(a, method)
+        # Check some simple shape mismatches
+        out = np.ones(11, dtype=np.int_)
+        assert_raises(ValueError, arg_method, -1, out)
+
+        out = np.ones((2, 5), dtype=np.int_)
+        assert_raises(ValueError, arg_method, -1, out)
+
+        # these could be relaxed possibly (used to allow even the previous)
+        out = np.ones((1, 10), dtype=np.int_)
+        assert_raises(ValueError, arg_method, -1, out)
+
+        out = np.ones(10, dtype=np.int_)
+        arg_method(-1, out=out)
+        assert_equal(out, arg_method(-1))
+
+    @pytest.mark.parametrize('ndim', [0, 1])
+    @pytest.mark.parametrize('method', ['argmax', 'argmin'])
+    def test_ret_is_out(self, ndim, method):
+        a = np.ones((4,) + (256,)*ndim)
+        arg_method = getattr(a, method)
+        out = np.empty((256,)*ndim, dtype=np.intp)
+        ret = arg_method(axis=0, out=out)
+        assert ret is out
+
+    @pytest.mark.parametrize('np_array, method, idx, val',
+        [(np.zeros, 'argmax', 5942, "as"),
+         (np.ones, 'argmin', 6001, "0")])
+    def test_unicode(self, np_array, method, idx, val):
+        d = np_array(6031, dtype='<U9')
+        arg_method = getattr(d, method)
+        d[idx] = val
+        assert_equal(arg_method(), idx)
+
+    @pytest.mark.parametrize('arr_method, np_method',
+        [('argmax', np.argmax),
+         ('argmin', np.argmin)])
+    def test_np_vs_ndarray(self, arr_method, np_method):
+        # make sure both ndarray.argmax/argmin and
+        # numpy.argmax/argmin support out/axis args
+        a = np.random.normal(size=(2, 3))
+        arg_method = getattr(a, arr_method)
+
+        # check positional args
+        out1 = np.zeros(2, dtype=int)
+        out2 = np.zeros(2, dtype=int)
+        assert_equal(arg_method(1, out1), np_method(a, 1, out2))
+        assert_equal(out1, out2)
+
+        # check keyword args
+        out1 = np.zeros(3, dtype=int)
+        out2 = np.zeros(3, dtype=int)
+        assert_equal(arg_method(out=out1, axis=0),
+                     np_method(a, out=out2, axis=0))
+        assert_equal(out1, out2)
+
+    @pytest.mark.leaks_references(reason="replaces None with NULL.")
+    @pytest.mark.parametrize('method, vals',
+        [('argmax', (10, 30)),
+         ('argmin', (30, 10))])
+    def test_object_with_NULLs(self, method, vals):
+        # See gh-6032
+        a = np.empty(4, dtype='O')
+        arg_method = getattr(a, method)
+        ctypes.memset(a.ctypes.data, 0, a.nbytes)
+        assert_equal(arg_method(), 0)
+        a[3] = vals[0]
+        assert_equal(arg_method(), 3)
+        a[1] = vals[1]
+        assert_equal(arg_method(), 1)
+
+class TestArgmax:
+    usg_data = [
+        ([1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0], 0),
+        ([3, 3, 3, 3,  2,  2,  2,  2], 0),
+        ([0, 1, 2, 3,  4,  5,  6,  7], 7),
+        ([7, 6, 5, 4,  3,  2,  1,  0], 0)
+    ]
+    sg_data = usg_data + [
+        ([1, 2, 3, 4, -4, -3, -2, -1], 3),
+        ([1, 2, 3, 4, -1, -2, -3, -4], 3)
+    ]
+    darr = [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product(usg_data, (
+            np.uint8, np.uint16, np.uint32, np.uint64
+        ))
+    )]
+    darr = darr + [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product(sg_data, (
+            np.int8, np.int16, np.int32, np.int64, np.float32, np.float64
+        ))
+    )]
+    darr = darr + [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product((
+            ([0, 1, 2, 3, np.nan], 4),
+            ([0, 1, 2, np.nan, 3], 3),
+            ([np.nan, 0, 1, 2, 3], 0),
+            ([np.nan, 0, np.nan, 2, 3], 0),
+            # To hit the tail of SIMD multi-level(x4, x1) inner loops
+            # on variant SIMD widthes
+            ([1] * (2*5-1) + [np.nan], 2*5-1),
+            ([1] * (4*5-1) + [np.nan], 4*5-1),
+            ([1] * (8*5-1) + [np.nan], 8*5-1),
+            ([1] * (16*5-1) + [np.nan], 16*5-1),
+            ([1] * (32*5-1) + [np.nan], 32*5-1)
+        ), (
+            np.float32, np.float64
+        ))
+    )]
+    nan_arr = darr + [
+        ([0, 1, 2, 3, complex(0, np.nan)], 4),
+        ([0, 1, 2, 3, complex(np.nan, 0)], 4),
+        ([0, 1, 2, complex(np.nan, 0), 3], 3),
+        ([0, 1, 2, complex(0, np.nan), 3], 3),
+        ([complex(0, np.nan), 0, 1, 2, 3], 0),
+        ([complex(np.nan, np.nan), 0, 1, 2, 3], 0),
+        ([complex(np.nan, 0), complex(np.nan, 2), complex(np.nan, 1)], 0),
+        ([complex(np.nan, np.nan), complex(np.nan, 2), complex(np.nan, 1)], 0),
+        ([complex(np.nan, 0), complex(np.nan, 2), complex(np.nan, np.nan)], 0),
+
+        ([complex(0, 0), complex(0, 2), complex(0, 1)], 1),
+        ([complex(1, 0), complex(0, 2), complex(0, 1)], 0),
+        ([complex(1, 0), complex(0, 2), complex(1, 1)], 2),
+
+        ([np.datetime64('1923-04-14T12:43:12'),
+          np.datetime64('1994-06-21T14:43:15'),
+          np.datetime64('2001-10-15T04:10:32'),
+          np.datetime64('1995-11-25T16:02:16'),
+          np.datetime64('2005-01-04T03:14:12'),
+          np.datetime64('2041-12-03T14:05:03')], 5),
+        ([np.datetime64('1935-09-14T04:40:11'),
+          np.datetime64('1949-10-12T12:32:11'),
+          np.datetime64('2010-01-03T05:14:12'),
+          np.datetime64('2015-11-20T12:20:59'),
+          np.datetime64('1932-09-23T10:10:13'),
+          np.datetime64('2014-10-10T03:50:30')], 3),
+        # Assorted tests with NaTs
+        ([np.datetime64('NaT'),
+          np.datetime64('NaT'),
+          np.datetime64('2010-01-03T05:14:12'),
+          np.datetime64('NaT'),
+          np.datetime64('2015-09-23T10:10:13'),
+          np.datetime64('1932-10-10T03:50:30')], 0),
+        ([np.datetime64('2059-03-14T12:43:12'),
+          np.datetime64('1996-09-21T14:43:15'),
+          np.datetime64('NaT'),
+          np.datetime64('2022-12-25T16:02:16'),
+          np.datetime64('1963-10-04T03:14:12'),
+          np.datetime64('2013-05-08T18:15:23')], 2),
+        ([np.timedelta64(2, 's'),
+          np.timedelta64(1, 's'),
+          np.timedelta64('NaT', 's'),
+          np.timedelta64(3, 's')], 2),
+        ([np.timedelta64('NaT', 's')] * 3, 0),
+
+        ([timedelta(days=5, seconds=14), timedelta(days=2, seconds=35),
+          timedelta(days=-1, seconds=23)], 0),
+        ([timedelta(days=1, seconds=43), timedelta(days=10, seconds=5),
+          timedelta(days=5, seconds=14)], 1),
+        ([timedelta(days=10, seconds=24), timedelta(days=10, seconds=5),
+          timedelta(days=10, seconds=43)], 2),
+
+        ([False, False, False, False, True], 4),
+        ([False, False, False, True, False], 3),
+        ([True, False, False, False, False], 0),
+        ([True, False, True, False, False], 0),
+    ]
+
+    @pytest.mark.parametrize('data', nan_arr)
+    def test_combinations(self, data):
+        arr, pos = data
+        with suppress_warnings() as sup:
+            sup.filter(RuntimeWarning,
+                        "invalid value encountered in reduce")
+            val = np.max(arr)
+
+        assert_equal(np.argmax(arr), pos, err_msg="%r" % arr)
+        assert_equal(arr[np.argmax(arr)], val, err_msg="%r" % arr)
+
+        # add padding to test SIMD loops
+        rarr = np.repeat(arr, 129)
+        rpos = pos * 129
+        assert_equal(np.argmax(rarr), rpos, err_msg="%r" % rarr)
+        assert_equal(rarr[np.argmax(rarr)], val, err_msg="%r" % rarr)
+
+        padd = np.repeat(np.min(arr), 513)
+        rarr = np.concatenate((arr, padd))
+        rpos = pos
+        assert_equal(np.argmax(rarr), rpos, err_msg="%r" % rarr)
+        assert_equal(rarr[np.argmax(rarr)], val, err_msg="%r" % rarr)
+
+
+    def test_maximum_signed_integers(self):
+
+        a = np.array([1, 2**7 - 1, -2**7], dtype=np.int8)
+        assert_equal(np.argmax(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmax(a), 129)
+
+        a = np.array([1, 2**15 - 1, -2**15], dtype=np.int16)
+        assert_equal(np.argmax(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmax(a), 129)
+
+        a = np.array([1, 2**31 - 1, -2**31], dtype=np.int32)
+        assert_equal(np.argmax(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmax(a), 129)
+
+        a = np.array([1, 2**63 - 1, -2**63], dtype=np.int64)
+        assert_equal(np.argmax(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmax(a), 129)
+
+class TestArgmin:
+    usg_data = [
+        ([1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0], 8),
+        ([3, 3, 3, 3,  2,  2,  2,  2], 4),
+        ([0, 1, 2, 3,  4,  5,  6,  7], 0),
+        ([7, 6, 5, 4,  3,  2,  1,  0], 7)
+    ]
+    sg_data = usg_data + [
+        ([1, 2, 3, 4, -4, -3, -2, -1], 4),
+        ([1, 2, 3, 4, -1, -2, -3, -4], 7)
+    ]
+    darr = [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product(usg_data, (
+            np.uint8, np.uint16, np.uint32, np.uint64
+        ))
+    )]
+    darr = darr + [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product(sg_data, (
+            np.int8, np.int16, np.int32, np.int64, np.float32, np.float64
+        ))
+    )]
+    darr = darr + [(np.array(d[0], dtype=t), d[1]) for d, t in (
+        itertools.product((
+            ([0, 1, 2, 3, np.nan], 4),
+            ([0, 1, 2, np.nan, 3], 3),
+            ([np.nan, 0, 1, 2, 3], 0),
+            ([np.nan, 0, np.nan, 2, 3], 0),
+            # To hit the tail of SIMD multi-level(x4, x1) inner loops
+            # on variant SIMD widthes
+            ([1] * (2*5-1) + [np.nan], 2*5-1),
+            ([1] * (4*5-1) + [np.nan], 4*5-1),
+            ([1] * (8*5-1) + [np.nan], 8*5-1),
+            ([1] * (16*5-1) + [np.nan], 16*5-1),
+            ([1] * (32*5-1) + [np.nan], 32*5-1)
+        ), (
+            np.float32, np.float64
+        ))
+    )]
+    nan_arr = darr + [
+        ([0, 1, 2, 3, complex(0, np.nan)], 4),
+        ([0, 1, 2, 3, complex(np.nan, 0)], 4),
+        ([0, 1, 2, complex(np.nan, 0), 3], 3),
+        ([0, 1, 2, complex(0, np.nan), 3], 3),
+        ([complex(0, np.nan), 0, 1, 2, 3], 0),
+        ([complex(np.nan, np.nan), 0, 1, 2, 3], 0),
+        ([complex(np.nan, 0), complex(np.nan, 2), complex(np.nan, 1)], 0),
+        ([complex(np.nan, np.nan), complex(np.nan, 2), complex(np.nan, 1)], 0),
+        ([complex(np.nan, 0), complex(np.nan, 2), complex(np.nan, np.nan)], 0),
+
+        ([complex(0, 0), complex(0, 2), complex(0, 1)], 0),
+        ([complex(1, 0), complex(0, 2), complex(0, 1)], 2),
+        ([complex(1, 0), complex(0, 2), complex(1, 1)], 1),
+
+        ([np.datetime64('1923-04-14T12:43:12'),
+          np.datetime64('1994-06-21T14:43:15'),
+          np.datetime64('2001-10-15T04:10:32'),
+          np.datetime64('1995-11-25T16:02:16'),
+          np.datetime64('2005-01-04T03:14:12'),
+          np.datetime64('2041-12-03T14:05:03')], 0),
+        ([np.datetime64('1935-09-14T04:40:11'),
+          np.datetime64('1949-10-12T12:32:11'),
+          np.datetime64('2010-01-03T05:14:12'),
+          np.datetime64('2014-11-20T12:20:59'),
+          np.datetime64('2015-09-23T10:10:13'),
+          np.datetime64('1932-10-10T03:50:30')], 5),
+        # Assorted tests with NaTs
+        ([np.datetime64('NaT'),
+          np.datetime64('NaT'),
+          np.datetime64('2010-01-03T05:14:12'),
+          np.datetime64('NaT'),
+          np.datetime64('2015-09-23T10:10:13'),
+          np.datetime64('1932-10-10T03:50:30')], 0),
+        ([np.datetime64('2059-03-14T12:43:12'),
+          np.datetime64('1996-09-21T14:43:15'),
+          np.datetime64('NaT'),
+          np.datetime64('2022-12-25T16:02:16'),
+          np.datetime64('1963-10-04T03:14:12'),
+          np.datetime64('2013-05-08T18:15:23')], 2),
+        ([np.timedelta64(2, 's'),
+          np.timedelta64(1, 's'),
+          np.timedelta64('NaT', 's'),
+          np.timedelta64(3, 's')], 2),
+        ([np.timedelta64('NaT', 's')] * 3, 0),
+
+        ([timedelta(days=5, seconds=14), timedelta(days=2, seconds=35),
+          timedelta(days=-1, seconds=23)], 2),
+        ([timedelta(days=1, seconds=43), timedelta(days=10, seconds=5),
+          timedelta(days=5, seconds=14)], 0),
+        ([timedelta(days=10, seconds=24), timedelta(days=10, seconds=5),
+          timedelta(days=10, seconds=43)], 1),
+
+        ([True, True, True, True, False], 4),
+        ([True, True, True, False, True], 3),
+        ([False, True, True, True, True], 0),
+        ([False, True, False, True, True], 0),
+    ]
+
+    @pytest.mark.parametrize('data', nan_arr)
+    def test_combinations(self, data):
+        arr, pos = data
+        with suppress_warnings() as sup:
+            sup.filter(RuntimeWarning,
+                       "invalid value encountered in reduce")
+            min_val = np.min(arr)
+
+        assert_equal(np.argmin(arr), pos, err_msg="%r" % arr)
+        assert_equal(arr[np.argmin(arr)], min_val, err_msg="%r" % arr)
+
+        # add padding to test SIMD loops
+        rarr = np.repeat(arr, 129)
+        rpos = pos * 129
+        assert_equal(np.argmin(rarr), rpos, err_msg="%r" % rarr)
+        assert_equal(rarr[np.argmin(rarr)], min_val, err_msg="%r" % rarr)
+
+        padd = np.repeat(np.max(arr), 513)
+        rarr = np.concatenate((arr, padd))
+        rpos = pos
+        assert_equal(np.argmin(rarr), rpos, err_msg="%r" % rarr)
+        assert_equal(rarr[np.argmin(rarr)], min_val, err_msg="%r" % rarr)
+
+    def test_minimum_signed_integers(self):
+
+        a = np.array([1, -2**7, -2**7 + 1, 2**7 - 1], dtype=np.int8)
+        assert_equal(np.argmin(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmin(a), 129)
+
+        a = np.array([1, -2**15, -2**15 + 1, 2**15 - 1], dtype=np.int16)
+        assert_equal(np.argmin(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmin(a), 129)
+
+        a = np.array([1, -2**31, -2**31 + 1, 2**31 - 1], dtype=np.int32)
+        assert_equal(np.argmin(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmin(a), 129)
+
+        a = np.array([1, -2**63, -2**63 + 1, 2**63 - 1], dtype=np.int64)
+        assert_equal(np.argmin(a), 1)
+        a = a.repeat(129)
+        assert_equal(np.argmin(a), 129)
+
+class TestMinMax:
+
+    def test_scalar(self):
+        assert_raises(np.AxisError, np.amax, 1, 1)
+        assert_raises(np.AxisError, np.amin, 1, 1)
+
+        assert_equal(np.amax(1, axis=0), 1)
+        assert_equal(np.amin(1, axis=0), 1)
+        assert_equal(np.amax(1, axis=None), 1)
+        assert_equal(np.amin(1, axis=None), 1)
+
+    def test_axis(self):
+        assert_raises(np.AxisError, np.amax, [1, 2, 3], 1000)
+        assert_equal(np.amax([[1, 2, 3]], axis=1), 3)
+
+    def test_datetime(self):
+        # Do not ignore NaT
+        for dtype in ('m8[s]', 'm8[Y]'):
+            a = np.arange(10).astype(dtype)
+            assert_equal(np.amin(a), a[0])
+            assert_equal(np.amax(a), a[9])
+            a[3] = 'NaT'
+            assert_equal(np.amin(a), a[3])
+            assert_equal(np.amax(a), a[3])
+
+
+class TestNewaxis:
+    def test_basic(self):
+        sk = np.array([0, -0.1, 0.1])
+        res = 250*sk[:, np.newaxis]
+        assert_almost_equal(res.ravel(), 250*sk)
+
+
+class TestClip:
+    def _check_range(self, x, cmin, cmax):
+        assert_(np.all(x >= cmin))
+        assert_(np.all(x <= cmax))
+
+    def _clip_type(self, type_group, array_max,
+                   clip_min, clip_max, inplace=False,
+                   expected_min=None, expected_max=None):
+        if expected_min is None:
+            expected_min = clip_min
+        if expected_max is None:
+            expected_max = clip_max
+
+        for T in np.sctypes[type_group]:
+            if sys.byteorder == 'little':
+                byte_orders = ['=', '>']
+            else:
+                byte_orders = ['<', '=']
+
+            for byteorder in byte_orders:
+                dtype = np.dtype(T).newbyteorder(byteorder)
+
+                x = (np.random.random(1000) * array_max).astype(dtype)
+                if inplace:
+                    # The tests that call us pass clip_min and clip_max that
+                    # might not fit in the destination dtype. They were written
+                    # assuming the previous unsafe casting, which now must be
+                    # passed explicitly to avoid a warning.
+                    x.clip(clip_min, clip_max, x, casting='unsafe')
+                else:
+                    x = x.clip(clip_min, clip_max)
+                    byteorder = '='
+
+                if x.dtype.byteorder == '|':
+                    byteorder = '|'
+                assert_equal(x.dtype.byteorder, byteorder)
+                self._check_range(x, expected_min, expected_max)
+        return x
+
+    def test_basic(self):
+        for inplace in [False, True]:
+            self._clip_type(
+                'float', 1024, -12.8, 100.2, inplace=inplace)
+            self._clip_type(
+                'float', 1024, 0, 0, inplace=inplace)
+
+            self._clip_type(
+                'int', 1024, -120, 100, inplace=inplace)
+            self._clip_type(
+                'int', 1024, 0, 0, inplace=inplace)
+
+            self._clip_type(
+                'uint', 1024, 0, 0, inplace=inplace)
+            self._clip_type(
+                'uint', 1024, -120, 100, inplace=inplace, expected_min=0)
+
+    def test_record_array(self):
+        rec = np.array([(-5, 2.0, 3.0), (5.0, 4.0, 3.0)],
+                       dtype=[('x', '<f8'), ('y', '<f8'), ('z', '<f8')])
+        y = rec['x'].clip(-0.3, 0.5)
+        self._check_range(y, -0.3, 0.5)
+
+    def test_max_or_min(self):
+        val = np.array([0, 1, 2, 3, 4, 5, 6, 7])
+        x = val.clip(3)
+        assert_(np.all(x >= 3))
+        x = val.clip(min=3)
+        assert_(np.all(x >= 3))
+        x = val.clip(max=4)
+        assert_(np.all(x <= 4))
+
+    def test_nan(self):
+        input_arr = np.array([-2., np.nan, 0.5, 3., 0.25, np.nan])
+        result = input_arr.clip(-1, 1)
+        expected = np.array([-1., np.nan, 0.5, 1., 0.25, np.nan])
+        assert_array_equal(result, expected)
+
+
+class TestCompress:
+    def test_axis(self):
+        tgt = [[5, 6, 7, 8, 9]]
+        arr = np.arange(10).reshape(2, 5)
+        out = np.compress([0, 1], arr, axis=0)
+        assert_equal(out, tgt)
+
+        tgt = [[1, 3], [6, 8]]
+        out = np.compress([0, 1, 0, 1, 0], arr, axis=1)
+        assert_equal(out, tgt)
+
+    def test_truncate(self):
+        tgt = [[1], [6]]
+        arr = np.arange(10).reshape(2, 5)
+        out = np.compress([0, 1], arr, axis=1)
+        assert_equal(out, tgt)
+
+    def test_flatten(self):
+        arr = np.arange(10).reshape(2, 5)
+        out = np.compress([0, 1], arr)
+        assert_equal(out, 1)
+
+
+class TestPutmask:
+    def tst_basic(self, x, T, mask, val):
+        np.putmask(x, mask, val)
+        assert_equal(x[mask], np.array(val, T))
+
+    def test_ip_types(self):
+        unchecked_types = [bytes, str, np.void]
+
+        x = np.random.random(1000)*100
+        mask = x < 40
+
+        for val in [-100, 0, 15]:
+            for types in np.sctypes.values():
+                for T in types:
+                    if T not in unchecked_types:
+                        if val < 0 and np.dtype(T).kind == "u":
+                            val = np.iinfo(T).max - 99
+                        self.tst_basic(x.copy().astype(T), T, mask, val)
+
+            # Also test string of a length which uses an untypical length
+            dt = np.dtype("S3")
+            self.tst_basic(x.astype(dt), dt.type, mask, dt.type(val)[:3])
+
+    def test_mask_size(self):
+        assert_raises(ValueError, np.putmask, np.array([1, 2, 3]), [True], 5)
+
+    @pytest.mark.parametrize('dtype', ('>i4', '<i4'))
+    def test_byteorder(self, dtype):
+        x = np.array([1, 2, 3], dtype)
+        np.putmask(x, [True, False, True], -1)
+        assert_array_equal(x, [-1, 2, -1])
+
+    def test_record_array(self):
+        # Note mixed byteorder.
+        rec = np.array([(-5, 2.0, 3.0), (5.0, 4.0, 3.0)],
+                      dtype=[('x', '<f8'), ('y', '>f8'), ('z', '<f8')])
+        np.putmask(rec['x'], [True, False], 10)
+        assert_array_equal(rec['x'], [10, 5])
+        assert_array_equal(rec['y'], [2, 4])
+        assert_array_equal(rec['z'], [3, 3])
+        np.putmask(rec['y'], [True, False], 11)
+        assert_array_equal(rec['x'], [10, 5])
+        assert_array_equal(rec['y'], [11, 4])
+        assert_array_equal(rec['z'], [3, 3])
+
+    def test_overlaps(self):
+        # gh-6272 check overlap
+        x = np.array([True, False, True, False])
+        np.putmask(x[1:4], [True, True, True], x[:3])
+        assert_equal(x, np.array([True, True, False, True]))
+
+        x = np.array([True, False, True, False])
+        np.putmask(x[1:4], x[:3], [True, False, True])
+        assert_equal(x, np.array([True, True, True, True]))
+
+    def test_writeable(self):
+        a = np.arange(5)
+        a.flags.writeable = False
+
+        with pytest.raises(ValueError):
+            np.putmask(a, a >= 2, 3)
+
+    def test_kwargs(self):
+        x = np.array([0, 0])
+        np.putmask(x, [0, 1], [-1, -2])
+        assert_array_equal(x, [0, -2])
+
+        x = np.array([0, 0])
+        np.putmask(x, mask=[0, 1], values=[-1, -2])
+        assert_array_equal(x, [0, -2])
+
+        x = np.array([0, 0])
+        np.putmask(x, values=[-1, -2],  mask=[0, 1])
+        assert_array_equal(x, [0, -2])
+
+        with pytest.raises(TypeError):
+            np.putmask(a=x, values=[-1, -2],  mask=[0, 1])
+
+
+class TestTake:
+    def tst_basic(self, x):
+        ind = list(range(x.shape[0]))
+        assert_array_equal(x.take(ind, axis=0), x)
+
+    def test_ip_types(self):
+        unchecked_types = [bytes, str, np.void]
+
+        x = np.random.random(24)*100
+        x.shape = 2, 3, 4
+        for types in np.sctypes.values():
+            for T in types:
+                if T not in unchecked_types:
+                    self.tst_basic(x.copy().astype(T))
+
+            # Also test string of a length which uses an untypical length
+            self.tst_basic(x.astype("S3"))
+
+    def test_raise(self):
+        x = np.random.random(24)*100
+        x.shape = 2, 3, 4
+        assert_raises(IndexError, x.take, [0, 1, 2], axis=0)
+        assert_raises(IndexError, x.take, [-3], axis=0)
+        assert_array_equal(x.take([-1], axis=0)[0], x[1])
+
+    def test_clip(self):
+        x = np.random.random(24)*100
+        x.shape = 2, 3, 4
+        assert_array_equal(x.take([-1], axis=0, mode='clip')[0], x[0])
+        assert_array_equal(x.take([2], axis=0, mode='clip')[0], x[1])
+
+    def test_wrap(self):
+        x = np.random.random(24)*100
+        x.shape = 2, 3, 4
+        assert_array_equal(x.take([-1], axis=0, mode='wrap')[0], x[1])
+        assert_array_equal(x.take([2], axis=0, mode='wrap')[0], x[0])
+        assert_array_equal(x.take([3], axis=0, mode='wrap')[0], x[1])
+
+    @pytest.mark.parametrize('dtype', ('>i4', '<i4'))
+    def test_byteorder(self, dtype):
+        x = np.array([1, 2, 3], dtype)
+        assert_array_equal(x.take([0, 2, 1]), [1, 3, 2])
+
+    def test_record_array(self):
+        # Note mixed byteorder.
+        rec = np.array([(-5, 2.0, 3.0), (5.0, 4.0, 3.0)],
+                      dtype=[('x', '<f8'), ('y', '>f8'), ('z', '<f8')])
+        rec1 = rec.take([1])
+        assert_(rec1['x'] == 5.0 and rec1['y'] == 4.0)
+
+    def test_out_overlap(self):
+        # gh-6272 check overlap on out
+        x = np.arange(5)
+        y = np.take(x, [1, 2, 3], out=x[2:5], mode='wrap')
+        assert_equal(y, np.array([1, 2, 3]))
+
+    @pytest.mark.parametrize('shape', [(1, 2), (1,), ()])
+    def test_ret_is_out(self, shape):
+        # 0d arrays should not be an exception to this rule
+        x = np.arange(5)
+        inds = np.zeros(shape, dtype=np.intp)
+        out = np.zeros(shape, dtype=x.dtype)
+        ret = np.take(x, inds, out=out)
+        assert ret is out
+
+
+class TestLexsort:
+    @pytest.mark.parametrize('dtype',[
+        np.uint8, np.uint16, np.uint32, np.uint64,
+        np.int8, np.int16, np.int32, np.int64,
+        np.float16, np.float32, np.float64
+    ])
+    def test_basic(self, dtype):
+        a = np.array([1, 2, 1, 3, 1, 5], dtype=dtype)
+        b = np.array([0, 4, 5, 6, 2, 3], dtype=dtype)
+        idx = np.lexsort((b, a))
+        expected_idx = np.array([0, 4, 2, 1, 3, 5])
+        assert_array_equal(idx, expected_idx)
+        assert_array_equal(a[idx], np.sort(a))
+
+    def test_mixed(self):
+        a = np.array([1, 2, 1, 3, 1, 5])
+        b = np.array([0, 4, 5, 6, 2, 3], dtype='datetime64[D]')
+
+        idx = np.lexsort((b, a))
+        expected_idx = np.array([0, 4, 2, 1, 3, 5])
+        assert_array_equal(idx, expected_idx)
+
+    def test_datetime(self):
+        a = np.array([0,0,0], dtype='datetime64[D]')
+        b = np.array([2,1,0], dtype='datetime64[D]')
+        idx = np.lexsort((b, a))
+        expected_idx = np.array([2, 1, 0])
+        assert_array_equal(idx, expected_idx)
+
+        a = np.array([0,0,0], dtype='timedelta64[D]')
+        b = np.array([2,1,0], dtype='timedelta64[D]')
+        idx = np.lexsort((b, a))
+        expected_idx = np.array([2, 1, 0])
+        assert_array_equal(idx, expected_idx)
+
+    def test_object(self):  # gh-6312
+        a = np.random.choice(10, 1000)
+        b = np.random.choice(['abc', 'xy', 'wz', 'efghi', 'qwst', 'x'], 1000)
+
+        for u in a, b:
+            left = np.lexsort((u.astype('O'),))
+            right = np.argsort(u, kind='mergesort')
+            assert_array_equal(left, right)
+
+        for u, v in (a, b), (b, a):
+            idx = np.lexsort((u, v))
+            assert_array_equal(idx, np.lexsort((u.astype('O'), v)))
+            assert_array_equal(idx, np.lexsort((u, v.astype('O'))))
+            u, v = np.array(u, dtype='object'), np.array(v, dtype='object')
+            assert_array_equal(idx, np.lexsort((u, v)))
+
+    def test_invalid_axis(self): # gh-7528
+        x = np.linspace(0., 1., 42*3).reshape(42, 3)
+        assert_raises(np.AxisError, np.lexsort, x, axis=2)
+
+class TestIO:
+    """Test tofile, fromfile, tobytes, and fromstring"""
+
+    @pytest.fixture()
+    def x(self):
+        shape = (2, 4, 3)
+        rand = np.random.random
+        x = rand(shape) + rand(shape).astype(complex) * 1j
+        x[0, :, 1] = [np.nan, np.inf, -np.inf, np.nan]
+        return x
+
+    @pytest.fixture(params=["string", "path_obj"])
+    def tmp_filename(self, tmp_path, request):
+        # This fixture covers two cases:
+        # one where the filename is a string and
+        # another where it is a pathlib object
+        filename = tmp_path / "file"
+        if request.param == "string":
+            filename = str(filename)
+        yield filename
+
+    def test_nofile(self):
+        # this should probably be supported as a file
+        # but for now test for proper errors
+        b = io.BytesIO()
+        assert_raises(OSError, np.fromfile, b, np.uint8, 80)
+        d = np.ones(7)
+        assert_raises(OSError, lambda x: x.tofile(b), d)
+
+    def test_bool_fromstring(self):
+        v = np.array([True, False, True, False], dtype=np.bool_)
+        y = np.fromstring('1 0 -2.3 0.0', sep=' ', dtype=np.bool_)
+        assert_array_equal(v, y)
+
+    def test_uint64_fromstring(self):
+        d = np.fromstring("9923372036854775807 104783749223640",
+                          dtype=np.uint64, sep=' ')
+        e = np.array([9923372036854775807, 104783749223640], dtype=np.uint64)
+        assert_array_equal(d, e)
+
+    def test_int64_fromstring(self):
+        d = np.fromstring("-25041670086757 104783749223640",
+                          dtype=np.int64, sep=' ')
+        e = np.array([-25041670086757, 104783749223640], dtype=np.int64)
+        assert_array_equal(d, e)
+
+    def test_fromstring_count0(self):
+        d = np.fromstring("1,2", sep=",", dtype=np.int64, count=0)
+        assert d.shape == (0,)
+
+    def test_empty_files_text(self, tmp_filename):
+        with open(tmp_filename, 'w') as f:
+            pass
+        y = np.fromfile(tmp_filename)
+        assert_(y.size == 0, "Array not empty")
+
+    def test_empty_files_binary(self, tmp_filename):
+        with open(tmp_filename, 'wb') as f:
+            pass
+        y = np.fromfile(tmp_filename, sep=" ")
+        assert_(y.size == 0, "Array not empty")
+
+    def test_roundtrip_file(self, x, tmp_filename):
+        with open(tmp_filename, 'wb') as f:
+            x.tofile(f)
+        # NB. doesn't work with flush+seek, due to use of C stdio
+        with open(tmp_filename, 'rb') as f:
+            y = np.fromfile(f, dtype=x.dtype)
+        assert_array_equal(y, x.flat)
+
+    def test_roundtrip(self, x, tmp_filename):
+        x.tofile(tmp_filename)
+        y = np.fromfile(tmp_filename, dtype=x.dtype)
+        assert_array_equal(y, x.flat)
+
+    def test_roundtrip_dump_pathlib(self, x, tmp_filename):
+        p = pathlib.Path(tmp_filename)
+        x.dump(p)
+        y = np.load(p, allow_pickle=True)
+        assert_array_equal(y, x)
+
+    def test_roundtrip_binary_str(self, x):
+        s = x.tobytes()
+        y = np.frombuffer(s, dtype=x.dtype)
+        assert_array_equal(y, x.flat)
+
+        s = x.tobytes('F')
+        y = np.frombuffer(s, dtype=x.dtype)
+        assert_array_equal(y, x.flatten('F'))
+
+    def test_roundtrip_str(self, x):
+        x = x.real.ravel()
+        s = "@".join(map(str, x))
+        y = np.fromstring(s, sep="@")
+        # NB. str imbues less precision
+        nan_mask = ~np.isfinite(x)
+        assert_array_equal(x[nan_mask], y[nan_mask])
+        assert_array_almost_equal(x[~nan_mask], y[~nan_mask], decimal=5)
+
+    def test_roundtrip_repr(self, x):
+        x = x.real.ravel()
+        s = "@".join(map(repr, x))
+        y = np.fromstring(s, sep="@")
+        assert_array_equal(x, y)
+
+    def test_unseekable_fromfile(self, x, tmp_filename):
+        # gh-6246
+        x.tofile(tmp_filename)
+
+        def fail(*args, **kwargs):
+            raise OSError('Can not tell or seek')
+
+        with io.open(tmp_filename, 'rb', buffering=0) as f:
+            f.seek = fail
+            f.tell = fail
+            assert_raises(OSError, np.fromfile, f, dtype=x.dtype)
+
+    def test_io_open_unbuffered_fromfile(self, x, tmp_filename):
+        # gh-6632
+        x.tofile(tmp_filename)
+        with io.open(tmp_filename, 'rb', buffering=0) as f:
+            y = np.fromfile(f, dtype=x.dtype)
+            assert_array_equal(y, x.flat)
+
+    def test_largish_file(self, tmp_filename):
+        # check the fallocate path on files > 16MB
+        d = np.zeros(4 * 1024 ** 2)
+        d.tofile(tmp_filename)
+        assert_equal(os.path.getsize(tmp_filename), d.nbytes)
+        assert_array_equal(d, np.fromfile(tmp_filename))
+        # check offset
+        with open(tmp_filename, "r+b") as f:
+            f.seek(d.nbytes)
+            d.tofile(f)
+            assert_equal(os.path.getsize(tmp_filename), d.nbytes * 2)
+        # check append mode (gh-8329)
+        open(tmp_filename, "w").close()  # delete file contents
+        with open(tmp_filename, "ab") as f:
+            d.tofile(f)
+        assert_array_equal(d, np.fromfile(tmp_filename))
+        with open(tmp_filename, "ab") as f:
+            d.tofile(f)
+        assert_equal(os.path.getsize(tmp_filename), d.nbytes * 2)
+
+    def test_io_open_buffered_fromfile(self, x, tmp_filename):
+        # gh-6632
+        x.tofile(tmp_filename)
+        with io.open(tmp_filename, 'rb', buffering=-1) as f:
+            y = np.fromfile(f, dtype=x.dtype)
+        assert_array_equal(y, x.flat)
+
+    def test_file_position_after_fromfile(self, tmp_filename):
+        # gh-4118
+        sizes = [io.DEFAULT_BUFFER_SIZE//8,
+                 io.DEFAULT_BUFFER_SIZE,
+                 io.DEFAULT_BUFFER_SIZE*8]
+
+        for size in sizes:
+            with open(tmp_filename, 'wb') as f:
+                f.seek(size-1)
+                f.write(b'\0')
+
+            for mode in ['rb', 'r+b']:
+                err_msg = "%d %s" % (size, mode)
+
+                with open(tmp_filename, mode) as f:
+                    f.read(2)
+                    np.fromfile(f, dtype=np.float64, count=1)
+                    pos = f.tell()
+                assert_equal(pos, 10, err_msg=err_msg)
+
+    def test_file_position_after_tofile(self, tmp_filename):
+        # gh-4118
+        sizes = [io.DEFAULT_BUFFER_SIZE//8,
+                 io.DEFAULT_BUFFER_SIZE,
+                 io.DEFAULT_BUFFER_SIZE*8]
+
+        for size in sizes:
+            err_msg = "%d" % (size,)
+
+            with open(tmp_filename, 'wb') as f:
+                f.seek(size-1)
+                f.write(b'\0')
+                f.seek(10)
+                f.write(b'12')
+                np.array([0], dtype=np.float64).tofile(f)
+                pos = f.tell()
+            assert_equal(pos, 10 + 2 + 8, err_msg=err_msg)
+
+            with open(tmp_filename, 'r+b') as f:
+                f.read(2)
+                f.seek(0, 1)  # seek between read&write required by ANSI C
+                np.array([0], dtype=np.float64).tofile(f)
+                pos = f.tell()
+            assert_equal(pos, 10, err_msg=err_msg)
+
+    def test_load_object_array_fromfile(self, tmp_filename):
+        # gh-12300
+        with open(tmp_filename, 'w') as f:
+            # Ensure we have a file with consistent contents
+            pass
+
+        with open(tmp_filename, 'rb') as f:
+            assert_raises_regex(ValueError, "Cannot read into object array",
+                                np.fromfile, f, dtype=object)
+
+        assert_raises_regex(ValueError, "Cannot read into object array",
+                            np.fromfile, tmp_filename, dtype=object)
+
+    def test_fromfile_offset(self, x, tmp_filename):
+        with open(tmp_filename, 'wb') as f:
+            x.tofile(f)
+
+        with open(tmp_filename, 'rb') as f:
+            y = np.fromfile(f, dtype=x.dtype, offset=0)
+            assert_array_equal(y, x.flat)
+
+        with open(tmp_filename, 'rb') as f:
+            count_items = len(x.flat) // 8
+            offset_items = len(x.flat) // 4
+            offset_bytes = x.dtype.itemsize * offset_items
+            y = np.fromfile(
+                f, dtype=x.dtype, count=count_items, offset=offset_bytes
+            )
+            assert_array_equal(
+                y, x.flat[offset_items:offset_items+count_items]
+            )
+
+            # subsequent seeks should stack
+            offset_bytes = x.dtype.itemsize
+            z = np.fromfile(f, dtype=x.dtype, offset=offset_bytes)
+            assert_array_equal(z, x.flat[offset_items+count_items+1:])
+
+        with open(tmp_filename, 'wb') as f:
+            x.tofile(f, sep=",")
+
+        with open(tmp_filename, 'rb') as f:
+            assert_raises_regex(
+                    TypeError,
+                    "'offset' argument only permitted for binary files",
+                    np.fromfile, tmp_filename, dtype=x.dtype,
+                    sep=",", offset=1)
+
+    @pytest.mark.skipif(IS_PYPY, reason="bug in PyPy's PyNumber_AsSsize_t")
+    def test_fromfile_bad_dup(self, x, tmp_filename):
+        def dup_str(fd):
+            return 'abc'
+
+        def dup_bigint(fd):
+            return 2**68
+
+        old_dup = os.dup
+        try:
+            with open(tmp_filename, 'wb') as f:
+                x.tofile(f)
+                for dup, exc in ((dup_str, TypeError), (dup_bigint, OSError)):
+                    os.dup = dup
+                    assert_raises(exc, np.fromfile, f)
+        finally:
+            os.dup = old_dup
+
+    def _check_from(self, s, value, filename, **kw):
+        if 'sep' not in kw:
+            y = np.frombuffer(s, **kw)
+        else:
+            y = np.fromstring(s, **kw)
+        assert_array_equal(y, value)
+
+        with open(filename, 'wb') as f:
+            f.write(s)
+        y = np.fromfile(filename, **kw)
+        assert_array_equal(y, value)
+
+    @pytest.fixture(params=["period", "comma"])
+    def decimal_sep_localization(self, request):
+        """
+        Including this fixture in a test will automatically
+        execute it with both types of decimal separator.
+
+        So::
+
+            def test_decimal(decimal_sep_localization):
+                pass
+
+        is equivalent to the following two tests::
+
+            def test_decimal_period_separator():
+                pass
+
+            def test_decimal_comma_separator():
+                with CommaDecimalPointLocale():
+                    pass
+        """
+        if request.param == "period":
+            yield
+        elif request.param == "comma":
+            with CommaDecimalPointLocale():
+                yield
+        else:
+            assert False, request.param
+
+    def test_nan(self, tmp_filename, decimal_sep_localization):
+        self._check_from(
+            b"nan +nan -nan NaN nan(foo) +NaN(BAR) -NAN(q_u_u_x_)",
+            [np.nan, np.nan, np.nan, np.nan, np.nan, np.nan, np.nan],
+            tmp_filename,
+            sep=' ')
+
+    def test_inf(self, tmp_filename, decimal_sep_localization):
+        self._check_from(
+            b"inf +inf -inf infinity -Infinity iNfInItY -inF",
+            [np.inf, np.inf, -np.inf, np.inf, -np.inf, np.inf, -np.inf],
+            tmp_filename,
+            sep=' ')
+
+    def test_numbers(self, tmp_filename, decimal_sep_localization):
+        self._check_from(
+            b"1.234 -1.234 .3 .3e55 -123133.1231e+133",
+            [1.234, -1.234, .3, .3e55, -123133.1231e+133],
+            tmp_filename,
+            sep=' ')
+
+    def test_binary(self, tmp_filename):
+        self._check_from(
+            b'\x00\x00\x80?\x00\x00\x00@\x00\x00@@\x00\x00\x80@',
+            np.array([1, 2, 3, 4]),
+            tmp_filename,
+            dtype='<f4')
+
+    def test_string(self, tmp_filename):
+        self._check_from(b'1,2,3,4', [1., 2., 3., 4.], tmp_filename, sep=',')
+
+    def test_counted_string(self, tmp_filename, decimal_sep_localization):
+        self._check_from(
+            b'1,2,3,4', [1., 2., 3., 4.], tmp_filename, count=4, sep=',')
+        self._check_from(
+            b'1,2,3,4', [1., 2., 3.], tmp_filename, count=3, sep=',')
+        self._check_from(
+            b'1,2,3,4', [1., 2., 3., 4.], tmp_filename, count=-1, sep=',')
+
+    def test_string_with_ws(self, tmp_filename):
+        self._check_from(
+            b'1 2  3     4   ', [1, 2, 3, 4], tmp_filename, dtype=int, sep=' ')
+
+    def test_counted_string_with_ws(self, tmp_filename):
+        self._check_from(
+            b'1 2  3     4   ', [1, 2, 3], tmp_filename, count=3, dtype=int,
+            sep=' ')
+
+    def test_ascii(self, tmp_filename, decimal_sep_localization):
+        self._check_from(
+            b'1 , 2 , 3 , 4', [1., 2., 3., 4.], tmp_filename, sep=',')
+        self._check_from(
+            b'1,2,3,4', [1., 2., 3., 4.], tmp_filename, dtype=float, sep=',')
+
+    def test_malformed(self, tmp_filename, decimal_sep_localization):
+        with assert_warns(DeprecationWarning):
+            self._check_from(
+                b'1.234 1,234', [1.234, 1.], tmp_filename, sep=' ')
+
+    def test_long_sep(self, tmp_filename):
+        self._check_from(
+            b'1_x_3_x_4_x_5', [1, 3, 4, 5], tmp_filename, sep='_x_')
+
+    def test_dtype(self, tmp_filename):
+        v = np.array([1, 2, 3, 4], dtype=np.int_)
+        self._check_from(b'1,2,3,4', v, tmp_filename, sep=',', dtype=np.int_)
+
+    def test_dtype_bool(self, tmp_filename):
+        # can't use _check_from because fromstring can't handle True/False
+        v = np.array([True, False, True, False], dtype=np.bool_)
+        s = b'1,0,-2.3,0'
+        with open(tmp_filename, 'wb') as f:
+            f.write(s)
+        y = np.fromfile(tmp_filename, sep=',', dtype=np.bool_)
+        assert_(y.dtype == '?')
+        assert_array_equal(y, v)
+
+    def test_tofile_sep(self, tmp_filename, decimal_sep_localization):
+        x = np.array([1.51, 2, 3.51, 4], dtype=float)
+        with open(tmp_filename, 'w') as f:
+            x.tofile(f, sep=',')
+        with open(tmp_filename, 'r') as f:
+            s = f.read()
+        #assert_equal(s, '1.51,2.0,3.51,4.0')
+        y = np.array([float(p) for p in s.split(',')])
+        assert_array_equal(x,y)
+
+    def test_tofile_format(self, tmp_filename, decimal_sep_localization):
+        x = np.array([1.51, 2, 3.51, 4], dtype=float)
+        with open(tmp_filename, 'w') as f:
+            x.tofile(f, sep=',', format='%.2f')
+        with open(tmp_filename, 'r') as f:
+            s = f.read()
+        assert_equal(s, '1.51,2.00,3.51,4.00')
+
+    def test_tofile_cleanup(self, tmp_filename):
+        x = np.zeros((10), dtype=object)
+        with open(tmp_filename, 'wb') as f:
+            assert_raises(OSError, lambda: x.tofile(f, sep=''))
+        # Dup-ed file handle should be closed or remove will fail on Windows OS
+        os.remove(tmp_filename)
+
+        # Also make sure that we close the Python handle
+        assert_raises(OSError, lambda: x.tofile(tmp_filename))
+        os.remove(tmp_filename)
+
+    def test_fromfile_subarray_binary(self, tmp_filename):
+        # Test subarray dtypes which are absorbed into the shape
+        x = np.arange(24, dtype="i4").reshape(2, 3, 4)
+        x.tofile(tmp_filename)
+        res = np.fromfile(tmp_filename, dtype="(3,4)i4")
+        assert_array_equal(x, res)
+
+        x_str = x.tobytes()
+        with assert_warns(DeprecationWarning):
+            # binary fromstring is deprecated
+            res = np.fromstring(x_str, dtype="(3,4)i4")
+            assert_array_equal(x, res)
+
+    def test_parsing_subarray_unsupported(self, tmp_filename):
+        # We currently do not support parsing subarray dtypes
+        data = "12,42,13," * 50
+        with pytest.raises(ValueError):
+            expected = np.fromstring(data, dtype="(3,)i", sep=",")
+
+        with open(tmp_filename, "w") as f:
+            f.write(data)
+
+        with pytest.raises(ValueError):
+            np.fromfile(tmp_filename, dtype="(3,)i", sep=",")
+
+    def test_read_shorter_than_count_subarray(self, tmp_filename):
+        # Test that requesting more values does not cause any problems
+        # in conjunction with subarray dimensions being absorbed into the
+        # array dimension.
+        expected = np.arange(511 * 10, dtype="i").reshape(-1, 10)
+
+        binary = expected.tobytes()
+        with pytest.raises(ValueError):
+            with pytest.warns(DeprecationWarning):
+                np.fromstring(binary, dtype="(10,)i", count=10000)
+
+        expected.tofile(tmp_filename)
+        res = np.fromfile(tmp_filename, dtype="(10,)i", count=10000)
+        assert_array_equal(res, expected)
+
+
+class TestFromBuffer:
+    @pytest.mark.parametrize('byteorder', ['<', '>'])
+    @pytest.mark.parametrize('dtype', [float, int, complex])
+    def test_basic(self, byteorder, dtype):
+        dt = np.dtype(dtype).newbyteorder(byteorder)
+        x = (np.random.random((4, 7)) * 5).astype(dt)
+        buf = x.tobytes()
+        assert_array_equal(np.frombuffer(buf, dtype=dt), x.flat)
+
+    @pytest.mark.parametrize("obj", [np.arange(10), b"12345678"])
+    def test_array_base(self, obj):
+        # Objects (including NumPy arrays), which do not use the
+        # `release_buffer` slot should be directly used as a base object.
+        # See also gh-21612
+        new = np.frombuffer(obj)
+        assert new.base is obj
+
+    def test_empty(self):
+        assert_array_equal(np.frombuffer(b''), np.array([]))
+
+    @pytest.mark.skipif(IS_PYPY,
+            reason="PyPy's memoryview currently does not track exports. See: "
+                   "https://foss.heptapod.net/pypy/pypy/-/issues/3724")
+    def test_mmap_close(self):
+        # The old buffer protocol was not safe for some things that the new
+        # one is.  But `frombuffer` always used the old one for a long time.
+        # Checks that it is safe with the new one (using memoryviews)
+        with tempfile.TemporaryFile(mode='wb') as tmp:
+            tmp.write(b"asdf")
+            tmp.flush()
+            mm = mmap.mmap(tmp.fileno(), 0)
+            arr = np.frombuffer(mm, dtype=np.uint8)
+            with pytest.raises(BufferError):
+                mm.close()  # cannot close while array uses the buffer
+            del arr
+            mm.close()
+
+class TestFlat:
+    def setup_method(self):
+        a0 = np.arange(20.0)
+        a = a0.reshape(4, 5)
+        a0.shape = (4, 5)
+        a.flags.writeable = False
+        self.a = a
+        self.b = a[::2, ::2]
+        self.a0 = a0
+        self.b0 = a0[::2, ::2]
+
+    def test_contiguous(self):
+        testpassed = False
+        try:
+            self.a.flat[12] = 100.0
+        except ValueError:
+            testpassed = True
+        assert_(testpassed)
+        assert_(self.a.flat[12] == 12.0)
+
+    def test_discontiguous(self):
+        testpassed = False
+        try:
+            self.b.flat[4] = 100.0
+        except ValueError:
+            testpassed = True
+        assert_(testpassed)
+        assert_(self.b.flat[4] == 12.0)
+
+    def test___array__(self):
+        c = self.a.flat.__array__()
+        d = self.b.flat.__array__()
+        e = self.a0.flat.__array__()
+        f = self.b0.flat.__array__()
+
+        assert_(c.flags.writeable is False)
+        assert_(d.flags.writeable is False)
+        assert_(e.flags.writeable is True)
+        assert_(f.flags.writeable is False)
+        assert_(c.flags.writebackifcopy is False)
+        assert_(d.flags.writebackifcopy is False)
+        assert_(e.flags.writebackifcopy is False)
+        assert_(f.flags.writebackifcopy is False)
+
+    @pytest.mark.skipif(not HAS_REFCOUNT, reason="Python lacks refcounts")
+    def test_refcount(self):
+        # includes regression test for reference count error gh-13165
+        inds = [np.intp(0), np.array([True]*self.a.size), np.array([0]), None]
+        indtype = np.dtype(np.intp)
+        rc_indtype = sys.getrefcount(indtype)
+        for ind in inds:
+            rc_ind = sys.getrefcount(ind)
+            for _ in range(100):
+                try:
+                    self.a.flat[ind]
+                except IndexError:
+                    pass
+            assert_(abs(sys.getrefcount(ind) - rc_ind) < 50)
+            assert_(abs(sys.getrefcount(indtype) - rc_indtype) < 50)
+
+    def test_index_getset(self):
+        it = np.arange(10).reshape(2, 1, 5).flat
+        with pytest.raises(AttributeError):
+            it.index = 10
+
+        for _ in it:
+            pass
+        # Check the value of `.index` is updated correctly (see also gh-19153)
+        # If the type was incorrect, this would show up on big-endian machines
+        assert it.index == it.base.size
+
+
+class TestResize:
+
+    @_no_tracing
+    def test_basic(self):
+        x = np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]])
+        if IS_PYPY:
+            x.resize((5, 5), refcheck=False)
+        else:
+            x.resize((5, 5))
+        assert_array_equal(x.flat[:9],
+                np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]]).flat)
+        assert_array_equal(x[9:].flat, 0)
+
+    def test_check_reference(self):
+        x = np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]])
+        y = x
+        assert_raises(ValueError, x.resize, (5, 1))
+        del y  # avoid pyflakes unused variable warning.
+
+    @_no_tracing
+    def test_int_shape(self):
+        x = np.eye(3)
+        if IS_PYPY:
+            x.resize(3, refcheck=False)
+        else:
+            x.resize(3)
+        assert_array_equal(x, np.eye(3)[0,:])
+
+    def test_none_shape(self):
+        x = np.eye(3)
+        x.resize(None)
+        assert_array_equal(x, np.eye(3))
+        x.resize()
+        assert_array_equal(x, np.eye(3))
+
+    def test_0d_shape(self):
+        # to it multiple times to test it does not break alloc cache gh-9216
+        for i in range(10):
+            x = np.empty((1,))
+            x.resize(())
+            assert_equal(x.shape, ())
+            assert_equal(x.size, 1)
+            x = np.empty(())
+            x.resize((1,))
+            assert_equal(x.shape, (1,))
+            assert_equal(x.size, 1)
+
+    def test_invalid_arguments(self):
+        assert_raises(TypeError, np.eye(3).resize, 'hi')
+        assert_raises(ValueError, np.eye(3).resize, -1)
+        assert_raises(TypeError, np.eye(3).resize, order=1)
+        assert_raises(TypeError, np.eye(3).resize, refcheck='hi')
+
+    @_no_tracing
+    def test_freeform_shape(self):
+        x = np.eye(3)
+        if IS_PYPY:
+            x.resize(3, 2, 1, refcheck=False)
+        else:
+            x.resize(3, 2, 1)
+        assert_(x.shape == (3, 2, 1))
+
+    @_no_tracing
+    def test_zeros_appended(self):
+        x = np.eye(3)
+        if IS_PYPY:
+            x.resize(2, 3, 3, refcheck=False)
+        else:
+            x.resize(2, 3, 3)
+        assert_array_equal(x[0], np.eye(3))
+        assert_array_equal(x[1], np.zeros((3, 3)))
+
+    @_no_tracing
+    def test_obj_obj(self):
+        # check memory is initialized on resize, gh-4857
+        a = np.ones(10, dtype=[('k', object, 2)])
+        if IS_PYPY:
+            a.resize(15, refcheck=False)
+        else:
+            a.resize(15,)
+        assert_equal(a.shape, (15,))
+        assert_array_equal(a['k'][-5:], 0)
+        assert_array_equal(a['k'][:-5], 1)
+
+    def test_empty_view(self):
+        # check that sizes containing a zero don't trigger a reallocate for
+        # already empty arrays
+        x = np.zeros((10, 0), int)
+        x_view = x[...]
+        x_view.resize((0, 10))
+        x_view.resize((0, 100))
+
+    def test_check_weakref(self):
+        x = np.array([[1, 0, 0], [0, 1, 0], [0, 0, 1]])
+        xref = weakref.ref(x)
+        assert_raises(ValueError, x.resize, (5, 1))
+        del xref  # avoid pyflakes unused variable warning.
+
+
+class TestRecord:
+    def test_field_rename(self):
+        dt = np.dtype([('f', float), ('i', int)])
+        dt.names = ['p', 'q']
+        assert_equal(dt.names, ['p', 'q'])
+
+    def test_multiple_field_name_occurrence(self):
+        def test_dtype_init():
+            np.dtype([("A", "f8"), ("B", "f8"), ("A", "f8")])
+
+        # Error raised when multiple fields have the same name
+        assert_raises(ValueError, test_dtype_init)
+
+    def test_bytes_fields(self):
+        # Bytes are not allowed in field names and not recognized in titles
+        # on Py3
+        assert_raises(TypeError, np.dtype, [(b'a', int)])
+        assert_raises(TypeError, np.dtype, [(('b', b'a'), int)])
+
+        dt = np.dtype([((b'a', 'b'), int)])
+        assert_raises(TypeError, dt.__getitem__, b'a')
+
+        x = np.array([(1,), (2,), (3,)], dtype=dt)
+        assert_raises(IndexError, x.__getitem__, b'a')
+
+        y = x[0]
+        assert_raises(IndexError, y.__getitem__, b'a')
+
+    def test_multiple_field_name_unicode(self):
+        def test_dtype_unicode():
+            np.dtype([("\u20B9", "f8"), ("B", "f8"), ("\u20B9", "f8")])
+
+        # Error raised when multiple fields have the same name(unicode included)
+        assert_raises(ValueError, test_dtype_unicode)
+
+    def test_fromarrays_unicode(self):
+        # A single name string provided to fromarrays() is allowed to be unicode
+        # on both Python 2 and 3:
+        x = np.core.records.fromarrays(
+            [[0], [1]], names='a,b', formats='i4,i4')
+        assert_equal(x['a'][0], 0)
+        assert_equal(x['b'][0], 1)
+
+    def test_unicode_order(self):
+        # Test that we can sort with order as a unicode field name in both Python 2 and
+        # 3:
+        name = 'b'
+        x = np.array([1, 3, 2], dtype=[(name, int)])
+        x.sort(order=name)
+        assert_equal(x['b'], np.array([1, 2, 3]))
+
+    def test_field_names(self):
+        # Test unicode and 8-bit / byte strings can be used
+        a = np.zeros((1,), dtype=[('f1', 'i4'),
+                                  ('f2', 'i4'),
+                                  ('f3', [('sf1', 'i4')])])
+        # byte string indexing fails gracefully
+        assert_raises(IndexError, a.__setitem__, b'f1', 1)
+        assert_raises(IndexError, a.__getitem__, b'f1')
+        assert_raises(IndexError, a['f1'].__setitem__, b'sf1', 1)
+        assert_raises(IndexError, a['f1'].__getitem__, b'sf1')
+        b = a.copy()
+        fn1 = str('f1')
+        b[fn1] = 1
+        assert_equal(b[fn1], 1)
+        fnn = str('not at all')
+        assert_raises(ValueError, b.__setitem__, fnn, 1)
+        assert_raises(ValueError, b.__getitem__, fnn)
+        b[0][fn1] = 2
+        assert_equal(b[fn1], 2)
+        # Subfield
+        assert_raises(ValueError, b[0].__setitem__, fnn, 1)
+        assert_raises(ValueError, b[0].__getitem__, fnn)
+        # Subfield
+        fn3 = str('f3')
+        sfn1 = str('sf1')
+        b[fn3][sfn1] = 1
+        assert_equal(b[fn3][sfn1], 1)
+        assert_raises(ValueError, b[fn3].__setitem__, fnn, 1)
+        assert_raises(ValueError, b[fn3].__getitem__, fnn)
+        # multiple subfields
+        fn2 = str('f2')
+        b[fn2] = 3
+
+        assert_equal(b[['f1', 'f2']][0].tolist(), (2, 3))
+        assert_equal(b[['f2', 'f1']][0].tolist(), (3, 2))
+        assert_equal(b[['f1', 'f3']][0].tolist(), (2, (1,)))
+
+        # non-ascii unicode field indexing is well behaved
+        assert_raises(ValueError, a.__setitem__, '\u03e0', 1)
+        assert_raises(ValueError, a.__getitem__, '\u03e0')
+
+    def test_record_hash(self):
+        a = np.array([(1, 2), (1, 2)], dtype='i1,i2')
+        a.flags.writeable = False
+        b = np.array([(1, 2), (3, 4)], dtype=[('num1', 'i1'), ('num2', 'i2')])
+        b.flags.writeable = False
+        c = np.array([(1, 2), (3, 4)], dtype='i1,i2')
+        c.flags.writeable = False
+        assert_(hash(a[0]) == hash(a[1]))
+        assert_(hash(a[0]) == hash(b[0]))
+        assert_(hash(a[0]) != hash(b[1]))
+        assert_(hash(c[0]) == hash(a[0]) and c[0] == a[0])
+
+    def test_record_no_hash(self):
+        a = np.array([(1, 2), (1, 2)], dtype='i1,i2')
+        assert_raises(TypeError, hash, a[0])
+
+    def test_empty_structure_creation(self):
+        # make sure these do not raise errors (gh-5631)
+        np.array([()], dtype={'names': [], 'formats': [],
+                           'offsets': [], 'itemsize': 12})
+        np.array([(), (), (), (), ()], dtype={'names': [], 'formats': [],
+                                           'offsets': [], 'itemsize': 12})
+
+    def test_multifield_indexing_view(self):
+        a = np.ones(3, dtype=[('a', 'i4'), ('b', 'f4'), ('c', 'u4')])
+        v = a[['a', 'c']]
+        assert_(v.base is a)
+        assert_(v.dtype == np.dtype({'names': ['a', 'c'],
+                                     'formats': ['i4', 'u4'],
+                                     'offsets': [0, 8]}))
+        v[:] = (4,5)
+        assert_equal(a[0].item(), (4, 1, 5))
+
+class TestView:
+    def test_basic(self):
+        x = np.array([(1, 2, 3, 4), (5, 6, 7, 8)],
+                     dtype=[('r', np.int8), ('g', np.int8),
+                            ('b', np.int8), ('a', np.int8)])
+        # We must be specific about the endianness here:
+        y = x.view(dtype='<i4')
+        # ... and again without the keyword.
+        z = x.view('<i4')
+        assert_array_equal(y, z)
+        assert_array_equal(y, [67305985, 134678021])
+
+
+def _mean(a, **args):
+    return a.mean(**args)
+
+
+def _var(a, **args):
+    return a.var(**args)
+
+
+def _std(a, **args):
+    return a.std(**args)
+
+
+class TestStats:
+
+    funcs = [_mean, _var, _std]
+
+    def setup_method(self):
+        np.random.seed(range(3))
+        self.rmat = np.random.random((4, 5))
+        self.cmat = self.rmat + 1j * self.rmat
+        self.omat = np.array([Decimal(repr(r)) for r in self.rmat.flat])
+        self.omat = self.omat.reshape(4, 5)
+
+    def test_python_type(self):
+        for x in (np.float16(1.), 1, 1., 1+0j):
+            assert_equal(np.mean([x]), 1.)
+            assert_equal(np.std([x]), 0.)
+            assert_equal(np.var([x]), 0.)
+
+    def test_keepdims(self):
+        mat = np.eye(3)
+        for f in self.funcs:
+            for axis in [0, 1]:
+                res = f(mat, axis=axis, keepdims=True)
+                assert_(res.ndim == mat.ndim)
+                assert_(res.shape[axis] == 1)
+            for axis in [None]:
+                res = f(mat, axis=axis, keepdims=True)
+                assert_(res.shape == (1, 1))
+
+    def test_out(self):
+        mat = np.eye(3)
+        for f in self.funcs:
+            out = np.zeros(3)
+            tgt = f(mat, axis=1)
+            res = f(mat, axis=1, out=out)
+            assert_almost_equal(res, out)
+            assert_almost_equal(res, tgt)
+        out = np.empty(2)
+        assert_raises(ValueError, f, mat, axis=1, out=out)
+        out = np.empty((2, 2))
+        assert_raises(ValueError, f, mat, axis=1, out=out)
+
+    def test_dtype_from_input(self):
+
+        icodes = np.typecodes['AllInteger']
+        fcodes = np.typecodes['AllFloat']
+
+        # object type
+        for f in self.funcs:
+            mat = np.array([[Decimal(1)]*3]*3)
+            tgt = mat.dtype.type
+            res = f(mat, axis=1).dtype.type
+            assert_(res is tgt)
+            # scalar case
+            res = type(f(mat, axis=None))
+            assert_(res is Decimal)
+
+        # integer types
+        for f in self.funcs:
+            for c in icodes:
+                mat = np.eye(3, dtype=c)
+                tgt = np.float64
+                res = f(mat, axis=1).dtype.type
+                assert_(res is tgt)
+                # scalar case
+                res = f(mat, axis=None).dtype.type
+                assert_(res is tgt)
+
+        # mean for float types
+        for f in [_mean]:
+            for c in fcodes:
+                mat = np.eye(3, dtype=c)
+                tgt = mat.dtype.type
+                res = f(mat, axis=1).dtype.type
+                assert_(res is tgt)
+                # scalar case
+                res = f(mat, axis=None).dtype.type
+                assert_(res is tgt)
+
+        # var, std for float types
+        for f in [_var, _std]:
+            for c in fcodes:
+                mat = np.eye(3, dtype=c)
+                # deal with complex types
+                tgt = mat.real.dtype.type
+                res = f(mat, axis=1).dtype.type
+                assert_(res is tgt)
+                # scalar case
+                res = f(mat, axis=None).dtype.type
+                assert_(res is tgt)
+
+    def test_dtype_from_dtype(self):
+        mat = np.eye(3)
+
+        # stats for integer types
+        # FIXME:
+        # this needs definition as there are lots places along the line
+        # where type casting may take place.
+
+        # for f in self.funcs:
+        #    for c in np.typecodes['AllInteger']:
+        #        tgt = np.dtype(c).type
+        #        res = f(mat, axis=1, dtype=c).dtype.type
+        #        assert_(res is tgt)
+        #        # scalar case
+        #        res = f(mat, axis=None, dtype=c).dtype.type
+        #        assert_(res is tgt)
+
+        # stats for float types
+        for f in self.funcs:
+            for c in np.typecodes['AllFloat']:
+                tgt = np.dtype(c).type
+                res = f(mat, axis=1, dtype=c).dtype.type
+                assert_(res is tgt)
+                # scalar case
+                res = f(mat, axis=None, dtype=c).dtype.type
+                assert_(res is tgt)
+
+    def test_ddof(self):
+        for f in [_var]:
+            for ddof in range(3):
+                dim = self.rmat.shape[1]
+                tgt = f(self.rmat, axis=1) * dim
+                res = f(self.rmat, axis=1, ddof=ddof) * (dim - ddof)
+        for f in [_std]:
+            for ddof in range(3):
+                dim = self.rmat.shape[1]
+                tgt = f(self.rmat, axis=1) * np.sqrt(dim)
+                res = f(self.rmat, axis=1, ddof=ddof) * np.sqrt(dim - ddof)
+                assert_almost_equal(res, tgt)
+                assert_almost_equal(res, tgt)
+
+    def test_ddof_too_big(self):
+        dim = self.rmat.shape[1]
+        for f in [_var, _std]:
+            for ddof in range(dim, dim + 2):
+                with warnings.catch_warnings(record=True) as w:
+                    warnings.simplefilter('always')
+                    res = f(self.rmat, axis=1, ddof=ddof)
+                    assert_(not (res < 0).any())
+                    assert_(len(w) > 0)
+                    assert_(issubclass(w[0].category, RuntimeWarning))
+
+    def test_empty(self):
+        A = np.zeros((0, 3))
+        for f in self.funcs:
+            for axis in [0, None]:
+                with warnings.catch_warnings(record=True) as w:
+                    warnings.simplefilter('always')
+                    assert_(np.isnan(f(A, axis=axis)).all())
+                    assert_(len(w) > 0)
+                    assert_(issubclass(w[0].category, RuntimeWarning))
+            for axis in [1]:
+                with warnings.catch_warnings(record=True) as w:
+                    warnings.simplefilter('always')
+                    assert_equal(f(A, axis=axis), np.zeros([]))
+
+    def test_mean_values(self):
+        for mat in [self.rmat, self.cmat, self.omat]:
+            for axis in [0, 1]:
+                tgt = mat.sum(axis=axis)
+                res = _mean(mat, axis=axis) * mat.shape[axis]
+                assert_almost_equal(res, tgt)
+            for axis in [None]:
+                tgt = mat.sum(axis=axis)
+                res = _mean(mat, axis=axis) * np.prod(mat.shape)
+                assert_almost_equal(res, tgt)
+
+    def test_mean_float16(self):
+        # This fail if the sum inside mean is done in float16 instead
+        # of float32.
+        assert_(_mean(np.ones(100000, dtype='float16')) == 1)
+
+    def test_mean_axis_error(self):
+        # Ensure that AxisError is raised instead of IndexError when axis is
+        # out of bounds, see gh-15817.
+        with assert_raises(np.exceptions.AxisError):
+            np.arange(10).mean(axis=2)
+
+    def test_mean_where(self):
+        a = np.arange(16).reshape((4, 4))
+        wh_full = np.array([[False, True, False, True],
+                            [True, False, True, False],
+                            [True, True, False, False],
+                            [False, False, True, True]])
+        wh_partial = np.array([[False],
+                               [True],
+                               [True],
+                               [False]])
+        _cases = [(1, True, [1.5, 5.5, 9.5, 13.5]),
+                  (0, wh_full, [6., 5., 10., 9.]),
+                  (1, wh_full, [2., 5., 8.5, 14.5]),
+                  (0, wh_partial, [6., 7., 8., 9.])]
+        for _ax, _wh, _res in _cases:
+            assert_allclose(a.mean(axis=_ax, where=_wh),
+                            np.array(_res))
+            assert_allclose(np.mean(a, axis=_ax, where=_wh),
+                            np.array(_res))
+
+        a3d = np.arange(16).reshape((2, 2, 4))
+        _wh_partial = np.array([False, True, True, False])
+        _res = [[1.5, 5.5], [9.5, 13.5]]
+        assert_allclose(a3d.mean(axis=2, where=_wh_partial),
+                        np.array(_res))
+        assert_allclose(np.mean(a3d, axis=2, where=_wh_partial),
+                        np.array(_res))
+
+        with pytest.warns(RuntimeWarning) as w:
+            assert_allclose(a.mean(axis=1, where=wh_partial),
+                            np.array([np.nan, 5.5, 9.5, np.nan]))
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(a.mean(where=False), np.nan)
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(np.mean(a, where=False), np.nan)
+
+    def test_var_values(self):
+        for mat in [self.rmat, self.cmat, self.omat]:
+            for axis in [0, 1, None]:
+                msqr = _mean(mat * mat.conj(), axis=axis)
+                mean = _mean(mat, axis=axis)
+                tgt = msqr - mean * mean.conjugate()
+                res = _var(mat, axis=axis)
+                assert_almost_equal(res, tgt)
+
+    @pytest.mark.parametrize(('complex_dtype', 'ndec'), (
+        ('complex64', 6),
+        ('complex128', 7),
+        ('clongdouble', 7),
+    ))
+    def test_var_complex_values(self, complex_dtype, ndec):
+        # Test fast-paths for every builtin complex type
+        for axis in [0, 1, None]:
+            mat = self.cmat.copy().astype(complex_dtype)
+            msqr = _mean(mat * mat.conj(), axis=axis)
+            mean = _mean(mat, axis=axis)
+            tgt = msqr - mean * mean.conjugate()
+            res = _var(mat, axis=axis)
+            assert_almost_equal(res, tgt, decimal=ndec)
+
+    def test_var_dimensions(self):
+        # _var paths for complex number introduce additions on views that
+        # increase dimensions. Ensure this generalizes to higher dims
+        mat = np.stack([self.cmat]*3)
+        for axis in [0, 1, 2, -1, None]:
+            msqr = _mean(mat * mat.conj(), axis=axis)
+            mean = _mean(mat, axis=axis)
+            tgt = msqr - mean * mean.conjugate()
+            res = _var(mat, axis=axis)
+            assert_almost_equal(res, tgt)
+
+    def test_var_complex_byteorder(self):
+        # Test that var fast-path does not cause failures for complex arrays
+        # with non-native byteorder
+        cmat = self.cmat.copy().astype('complex128')
+        cmat_swapped = cmat.astype(cmat.dtype.newbyteorder())
+        assert_almost_equal(cmat.var(), cmat_swapped.var())
+
+    def test_var_axis_error(self):
+        # Ensure that AxisError is raised instead of IndexError when axis is
+        # out of bounds, see gh-15817.
+        with assert_raises(np.exceptions.AxisError):
+            np.arange(10).var(axis=2)
+
+    def test_var_where(self):
+        a = np.arange(25).reshape((5, 5))
+        wh_full = np.array([[False, True, False, True, True],
+                            [True, False, True, True, False],
+                            [True, True, False, False, True],
+                            [False, True, True, False, True],
+                            [True, False, True, True, False]])
+        wh_partial = np.array([[False],
+                               [True],
+                               [True],
+                               [False],
+                               [True]])
+        _cases = [(0, True, [50., 50., 50., 50., 50.]),
+                  (1, True, [2., 2., 2., 2., 2.])]
+        for _ax, _wh, _res in _cases:
+            assert_allclose(a.var(axis=_ax, where=_wh),
+                            np.array(_res))
+            assert_allclose(np.var(a, axis=_ax, where=_wh),
+                            np.array(_res))
+
+        a3d = np.arange(16).reshape((2, 2, 4))
+        _wh_partial = np.array([False, True, True, False])
+        _res = [[0.25, 0.25], [0.25, 0.25]]
+        assert_allclose(a3d.var(axis=2, where=_wh_partial),
+                        np.array(_res))
+        assert_allclose(np.var(a3d, axis=2, where=_wh_partial),
+                        np.array(_res))
+
+        assert_allclose(np.var(a, axis=1, where=wh_full),
+                        np.var(a[wh_full].reshape((5, 3)), axis=1))
+        assert_allclose(np.var(a, axis=0, where=wh_partial),
+                        np.var(a[wh_partial[:,0]], axis=0))
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(a.var(where=False), np.nan)
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(np.var(a, where=False), np.nan)
+
+    def test_std_values(self):
+        for mat in [self.rmat, self.cmat, self.omat]:
+            for axis in [0, 1, None]:
+                tgt = np.sqrt(_var(mat, axis=axis))
+                res = _std(mat, axis=axis)
+                assert_almost_equal(res, tgt)
+
+    def test_std_where(self):
+        a = np.arange(25).reshape((5,5))[::-1]
+        whf = np.array([[False, True, False, True, True],
+                        [True, False, True, False, True],
+                        [True, True, False, True, False],
+                        [True, False, True, True, False],
+                        [False, True, False, True, True]])
+        whp = np.array([[False],
+                        [False],
+                        [True],
+                        [True],
+                        [False]])
+        _cases = [
+            (0, True, 7.07106781*np.ones((5))),
+            (1, True, 1.41421356*np.ones((5))),
+            (0, whf,
+             np.array([4.0824829 , 8.16496581, 5., 7.39509973, 8.49836586])),
+            (0, whp, 2.5*np.ones((5)))
+        ]
+        for _ax, _wh, _res in _cases:
+            assert_allclose(a.std(axis=_ax, where=_wh), _res)
+            assert_allclose(np.std(a, axis=_ax, where=_wh), _res)
+
+        a3d = np.arange(16).reshape((2, 2, 4))
+        _wh_partial = np.array([False, True, True, False])
+        _res = [[0.5, 0.5], [0.5, 0.5]]
+        assert_allclose(a3d.std(axis=2, where=_wh_partial),
+                        np.array(_res))
+        assert_allclose(np.std(a3d, axis=2, where=_wh_partial),
+                        np.array(_res))
+
+        assert_allclose(a.std(axis=1, where=whf),
+                        np.std(a[whf].reshape((5,3)), axis=1))
+        assert_allclose(np.std(a, axis=1, where=whf),
+                        (a[whf].reshape((5,3))).std(axis=1))
+        assert_allclose(a.std(axis=0, where=whp),
+                        np.std(a[whp[:,0]], axis=0))
+        assert_allclose(np.std(a, axis=0, where=whp),
+                        (a[whp[:,0]]).std(axis=0))
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(a.std(where=False), np.nan)
+        with pytest.warns(RuntimeWarning) as w:
+            assert_equal(np.std(a, where=False), np.nan)
+
+    def test_subclass(self):
+        class TestArray(np.ndarray):
+            def __new__(cls, data, info):
+                result = np.array(data)
+                result = result.view(cls)
+                result.info = info
+                return result
+
+            def __array_finalize__(self, obj):
+                self.info = getattr(obj, "info", '')
+
+        dat = TestArray([[1, 2, 3, 4], [5, 6, 7, 8]], 'jubba')
+        res = dat.mean(1)
+        assert_(res.info == dat.info)
+        res = dat.std(1)
+        assert_(res.info == dat.info)
+        res = dat.var(1)
+        assert_(res.info == dat.info)
+
+
+class TestVdot:
+    def test_basic(self):
+        dt_numeric = np.typecodes['AllFloat'] + np.typecodes['AllInteger']
+        dt_complex = np.typecodes['Complex']
+
+        # test real
+        a = np.eye(3)
+        for dt in dt_numeric + 'O':
+            b = a.astype(dt)
+            res = np.vdot(b, b)
+            assert_(np.isscalar(res))
+            assert_equal(np.vdot(b, b), 3)
+
+        # test complex
+        a = np.eye(3) * 1j
+        for dt in dt_complex + 'O':
+            b = a.astype(dt)
+            res = np.vdot(b, b)
+            assert_(np.isscalar(res))
+            assert_equal(np.vdot(b, b), 3)
+
+        # test boolean
+        b = np.eye(3, dtype=bool)
+        res = np.vdot(b, b)
+        assert_(np.isscalar(res))
+        assert_equal(np.vdot(b, b), True)
+
+    def test_vdot_array_order(self):
+        a = np.array([[1, 2], [3, 4]], order='C')
+        b = np.array([[1, 2], [3, 4]], order='F')
+        res = np.vdot(a, a)
+
+        # integer arrays are exact
+        assert_equal(np.vdot(a, b), res)
+        assert_equal(np.vdot(b, a), res)
+        assert_equal(np.vdot(b, b), res)
+
+    def test_vdot_uncontiguous(self):
+        for size in [2, 1000]:
+            # Different sizes match different branches in vdot.
+            a = np.zeros((size, 2, 2))
+            b = np.zeros((size, 2, 2))
+            a[:, 0, 0] = np.arange(size)
+            b[:, 0, 0] = np.arange(size) + 1
+            # Make a and b uncontiguous:
+            a = a[..., 0]
+            b = b[..., 0]
+
+            assert_equal(np.vdot(a, b),
+                         np.vdot(a.flatten(), b.flatten()))
+            assert_equal(np.vdot(a, b.copy()),
+                         np.vdot(a.flatten(), b.flatten()))
+            assert_equal(np.vdot(a.copy(), b),
+                         np.vdot(a.flatten(), b.flatten()))
+            assert_equal(np.vdot(a.copy('F'), b),
+                         np.vdot(a.flatten(), b.flatten()))
+            assert_equal(np.vdot(a, b.copy('F')),
+                         np.vdot(a.flatten(), b.flatten()))
+
+
+class TestDot:
+    def setup_method(self):
+        np.random.seed(128)
+        self.A = np.random.rand(4, 2)
+        self.b1 = np.random.rand(2, 1)
+        self.b2 = np.random.rand(2)
+        self.b3 = np.random.rand(1, 2)
+        self.b4 = np.random.rand(4)
+        self.N = 7
+
+    def test_dotmatmat(self):
+        A = self.A
+        res = np.dot(A.transpose(), A)
+        tgt = np.array([[1.45046013, 0.86323640],
+                        [0.86323640, 0.84934569]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotmatvec(self):
+        A, b1 = self.A, self.b1
+        res = np.dot(A, b1)
+        tgt = np.array([[0.32114320], [0.04889721],
+                        [0.15696029], [0.33612621]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotmatvec2(self):
+        A, b2 = self.A, self.b2
+        res = np.dot(A, b2)
+        tgt = np.array([0.29677940, 0.04518649, 0.14468333, 0.31039293])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecmat(self):
+        A, b4 = self.A, self.b4
+        res = np.dot(b4, A)
+        tgt = np.array([1.23495091, 1.12222648])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecmat2(self):
+        b3, A = self.b3, self.A
+        res = np.dot(b3, A.transpose())
+        tgt = np.array([[0.58793804, 0.08957460, 0.30605758, 0.62716383]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecmat3(self):
+        A, b4 = self.A, self.b4
+        res = np.dot(A.transpose(), b4)
+        tgt = np.array([1.23495091, 1.12222648])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecvecouter(self):
+        b1, b3 = self.b1, self.b3
+        res = np.dot(b1, b3)
+        tgt = np.array([[0.20128610, 0.08400440], [0.07190947, 0.03001058]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecvecinner(self):
+        b1, b3 = self.b1, self.b3
+        res = np.dot(b3, b1)
+        tgt = np.array([[ 0.23129668]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotcolumnvect1(self):
+        b1 = np.ones((3, 1))
+        b2 = [5.3]
+        res = np.dot(b1, b2)
+        tgt = np.array([5.3, 5.3, 5.3])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotcolumnvect2(self):
+        b1 = np.ones((3, 1)).transpose()
+        b2 = [6.2]
+        res = np.dot(b2, b1)
+        tgt = np.array([6.2, 6.2, 6.2])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecscalar(self):
+        np.random.seed(100)
+        b1 = np.random.rand(1, 1)
+        b2 = np.random.rand(1, 4)
+        res = np.dot(b1, b2)
+        tgt = np.array([[0.15126730, 0.23068496, 0.45905553, 0.00256425]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_dotvecscalar2(self):
+        np.random.seed(100)
+        b1 = np.random.rand(4, 1)
+        b2 = np.random.rand(1, 1)
+        res = np.dot(b1, b2)
+        tgt = np.array([[0.00256425],[0.00131359],[0.00200324],[ 0.00398638]])
+        assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_all(self):
+        dims = [(), (1,), (1, 1)]
+        dout = [(), (1,), (1, 1), (1,), (), (1,), (1, 1), (1,), (1, 1)]
+        for dim, (dim1, dim2) in zip(dout, itertools.product(dims, dims)):
+            b1 = np.zeros(dim1)
+            b2 = np.zeros(dim2)
+            res = np.dot(b1, b2)
+            tgt = np.zeros(dim)
+            assert_(res.shape == tgt.shape)
+            assert_almost_equal(res, tgt, decimal=self.N)
+
+    def test_vecobject(self):
+        class Vec:
+            def __init__(self, sequence=None):
+                if sequence is None:
+                    sequence = []
+                self.array = np.array(sequence)
+
+            def __add__(self, other):
+                out = Vec()
+                out.array = self.array + other.array
+                return out
+
+            def __sub__(self, other):
+                out = Vec()
+                out.array = self.array - other.array
+                return out
+
+            def __mul__(self, other):  # with scalar
+                out = Vec(self.array.copy())
+                out.array *= other
+                return out
+
+            def __rmul__(self, other):
+                return self*other
+
+        U_non_cont = np.transpose([[1., 1.], [1., 2.]])
+        U_cont = np.ascontiguousarray(U_non_cont)
+        x = np.array([Vec([1., 0.]), Vec([0., 1.])])
+        zeros = np.array([Vec([0., 0.]), Vec([0., 0.])])
+        zeros_test = np.dot(U_cont, x) - np.dot(U_non_cont, x)
+        assert_equal(zeros[0].array, zeros_test[0].array)
+        assert_equal(zeros[1].array, zeros_test[1].array)
+
+    def test_dot_2args(self):
+        from numpy.core.multiarray import dot
+
+        a = np.array([[1, 2], [3, 4]], dtype=float)
+        b = np.array([[1, 0], [1, 1]], dtype=float)
+        c = np.array([[3, 2], [7, 4]], dtype=float)
+
+        d = dot(a, b)
+        assert_allclose(c, d)
+
+    def test_dot_3args(self):
+        from numpy.core.multiarray import dot
+
+        np.random.seed(22)
+        f = np.random.random_sample((1024, 16))
+        v = np.random.random_sample((16, 32))
+
+        r = np.empty((1024, 32))
+        for i in range(12):
+            dot(f, v, r)
+        if HAS_REFCOUNT:
+            assert_equal(sys.getrefcount(r), 2)
+        r2 = dot(f, v, out=None)
+        assert_array_equal(r2, r)
+        assert_(r is dot(f, v, out=r))
+
+        v = v[:, 0].copy()  # v.shape == (16,)
+        r = r[:, 0].copy()  # r.shape == (1024,)
+        r2 = dot(f, v)
+        assert_(r is dot(f, v, r))
+        assert_array_equal(r2, r)
+
+    def test_dot_3args_errors(self):
+        from numpy.core.multiarray import dot
+
+        np.random.seed(22)
+        f = np.random.random_sample((1024, 16))
+        v = np.random.random_sample((16, 32))
+
+        r = np.empty((1024, 31))
+        assert_raises(ValueError, dot, f, v, r)
+
+        r = np.empty((1024,))
+        assert_raises(ValueError, dot, f, v, r)
+
+        r = np.empty((32,))
+        assert_raises(ValueError, dot, f, v, r)
+
+        r = np.empty((32, 1024))
+        assert_raises(ValueError, dot, f, v, r)
+        assert_raises(ValueError, dot, f, v, r.T)
+
+        r = np.empty((1024, 64))
+        assert_raises(ValueError, dot, f, v, r[:, ::2])
+        assert_raises(ValueError, dot, f, v, r[:, :32])
+
+        r = np.empty((1024, 32), dtype=np.float32)
+        assert_raises(ValueError, dot, f, v, r)
+
+        r = np.empty((1024, 32), dtype=int)
+        assert_raises(ValueError, dot, f, v, r)
+
+    def test_dot_out_result(self):
+        x = np.ones((), dtype=np.float16)
+        y = np.ones((5,), dtype=np.float16)
+        z = np.zeros((5,), dtype=np.float16)
+        res = x.dot(y, out=z)
+        assert np.array_equal(res, y)
+        assert np.array_equal(z, y)
+
+    def test_dot_out_aliasing(self):
+        x = np.ones((), dtype=np.float16)
+        y = np.ones((5,), dtype=np.float16)
+        z = np.zeros((5,), dtype=np.float16)
+        res = x.dot(y, out=z)
+        z[0] = 2
+        assert np.array_equal(res, z)
+
+    def test_dot_array_order(self):
+        a = np.array([[1, 2], [3, 4]], order='C')
+        b = np.array([[1, 2], [3, 4]], order='F')
+        res = np.dot(a, a)
+
+        # integer arrays are exact
+        assert_equal(np.dot(a, b), res)
+        assert_equal(np.dot(b, a), res)
+        assert_equal(np.dot(b, b), res)
+
+    def test_accelerate_framework_sgemv_fix(self):
+
+        def aligned_array(shape, align, dtype, order='C'):
+            d = dtype(0)
+            N = np.prod(shape)
+            tmp = np.zeros(N * d.nbytes + align, dtype=np.uint8)
+            address = tmp.__array_interface__["data"][0]
+            for offset in range(align):
+                if (address + offset) % align == 0:
+                    break
+            tmp = tmp[offset:offset+N*d.nbytes].view(dtype=dtype)
+            return tmp.reshape(shape, order=order)
+
+        def as_aligned(arr, align, dtype, order='C'):
+            aligned = aligned_array(arr.shape, align, dtype, order)
+            aligned[:] = arr[:]
+            return aligned
+
+        def assert_dot_close(A, X, desired):
+            assert_allclose(np.dot(A, X), desired, rtol=1e-5, atol=1e-7)
+
+        m = aligned_array(100, 15, np.float32)
+        s = aligned_array((100, 100), 15, np.float32)
+        np.dot(s, m)  # this will always segfault if the bug is present
+
+        testdata = itertools.product((15, 32), (10000,), (200, 89), ('C', 'F'))
+        for align, m, n, a_order in testdata:
+            # Calculation in double precision
+            A_d = np.random.rand(m, n)
+            X_d = np.random.rand(n)
+            desired = np.dot(A_d, X_d)
+            # Calculation with aligned single precision
+            A_f = as_aligned(A_d, align, np.float32, order=a_order)
+            X_f = as_aligned(X_d, align, np.float32)
+            assert_dot_close(A_f, X_f, desired)
+            # Strided A rows
+            A_d_2 = A_d[::2]
+            desired = np.dot(A_d_2, X_d)
+            A_f_2 = A_f[::2]
+            assert_dot_close(A_f_2, X_f, desired)
+            # Strided A columns, strided X vector
+            A_d_22 = A_d_2[:, ::2]
+            X_d_2 = X_d[::2]
+            desired = np.dot(A_d_22, X_d_2)
+            A_f_22 = A_f_2[:, ::2]
+            X_f_2 = X_f[::2]
+            assert_dot_close(A_f_22, X_f_2, desired)
+            # Check the strides are as expected
+            if a_order == 'F':
+                assert_equal(A_f_22.strides, (8, 8 * m))
+            else:
+                assert_equal(A_f_22.strides, (8 * n, 8))
+            assert_equal(X_f_2.strides, (8,))
+            # Strides in A rows + cols only
+            X_f_2c = as_aligned(X_f_2, align, np.float32)
+            assert_dot_close(A_f_22, X_f_2c, desired)
+            # Strides just in A cols
+            A_d_12 = A_d[:, ::2]
+            desired = np.dot(A_d_12, X_d_2)
+            A_f_12 = A_f[:, ::2]
+            assert_dot_close(A_f_12, X_f_2c, desired)
+            # Strides in A cols and X
+            assert_dot_close(A_f_12, X_f_2, desired)
+
+    @pytest.mark.slow
+    @pytest.mark.parametrize("dtype", [np.float64, np.complex128])
+    @requires_memory(free_bytes=18e9)  # complex case needs 18GiB+
+    def test_huge_vectordot(self, dtype):
+        # Large vector multiplications are chunked with 32bit BLAS
+        # Test that the chunking does the right thing, see also gh-22262
+        data = np.ones(2**30+100, dtype=dtype)
+        res = np.dot(data, data)
+        assert res == 2**30+100
+
+    def test_dtype_discovery_fails(self):
+        # See gh-14247, error checking was missing for failed dtype discovery
+        class BadObject(object):
+            def __array__(self):
+                raise TypeError("just this tiny mint leaf")
+
+        with pytest.raises(TypeError):
+            np.dot(BadObject(), BadObject())
+
+        with pytest.raises(TypeError):
+            np.dot(3.0, BadObject())
+
+
+class MatmulCommon:
+    """Common tests for '@' operator and numpy.matmul.
+
+    """
+    # Should work with these types. Will want to add
+    # "O" at some point
+    types = "?bhilqBHILQefdgFDGO"
+
+    def test_exceptions(self):
+        dims = [
+            ((1,), (2,)),            # mismatched vector vector
+            ((2, 1,), (2,)),         # mismatched matrix vector
+            ((2,), (1, 2)),          # mismatched vector matrix
+            ((1, 2), (3, 1)),        # mismatched matrix matrix
+            ((1,), ()),              # vector scalar
+            ((), (1)),               # scalar vector
+            ((1, 1), ()),            # matrix scalar
+            ((), (1, 1)),            # scalar matrix
+            ((2, 2, 1), (3, 1, 2)),  # cannot broadcast
+            ]
+
+        for dt, (dm1, dm2) in itertools.product(self.types, dims):
+            a = np.ones(dm1, dtype=dt)
+            b = np.ones(dm2, dtype=dt)
+            assert_raises(ValueError, self.matmul, a, b)
+
+    def test_shapes(self):
+        dims = [
+            ((1, 1), (2, 1, 1)),     # broadcast first argument
+            ((2, 1, 1), (1, 1)),     # broadcast second argument
+            ((2, 1, 1), (2, 1, 1)),  # matrix stack sizes match
+            ]
+
+        for dt, (dm1, dm2) in itertools.product(self.types, dims):
+            a = np.ones(dm1, dtype=dt)
+            b = np.ones(dm2, dtype=dt)
+            res = self.matmul(a, b)
+            assert_(res.shape == (2, 1, 1))
+
+        # vector vector returns scalars.
+        for dt in self.types:
+            a = np.ones((2,), dtype=dt)
+            b = np.ones((2,), dtype=dt)
+            c = self.matmul(a, b)
+            assert_(np.array(c).shape == ())
+
+    def test_result_types(self):
+        mat = np.ones((1,1))
+        vec = np.ones((1,))
+        for dt in self.types:
+            m = mat.astype(dt)
+            v = vec.astype(dt)
+            for arg in [(m, v), (v, m), (m, m)]:
+                res = self.matmul(*arg)
+                assert_(res.dtype == dt)
+
+            # vector vector returns scalars
+            if dt != "O":
+                res = self.matmul(v, v)
+                assert_(type(res) is np.dtype(dt).type)
+
+    def test_scalar_output(self):
+        vec1 = np.array([2])
+        vec2 = np.array([3, 4]).reshape(1, -1)
+        tgt = np.array([6, 8])
+        for dt in self.types[1:]:
+            v1 = vec1.astype(dt)
+            v2 = vec2.astype(dt)
+            res = self.matmul(v1, v2)
+            assert_equal(res, tgt)
+            res = self.matmul(v2.T, v1)
+            assert_equal(res, tgt)
+
+        # boolean type
+        vec = np.array([True, True], dtype='?').reshape(1, -1)
+        res = self.matmul(vec[:, 0], vec)
+        assert_equal(res, True)
+
+    def test_vector_vector_values(self):
+        vec1 = np.array([1, 2])
+        vec2 = np.array([3, 4]).reshape(-1, 1)
+        tgt1 = np.array([11])
+        tgt2 = np.array([[3, 6], [4, 8]])
+        for dt in self.types[1:]:
+            v1 = vec1.astype(dt)
+            v2 = vec2.astype(dt)
+            res = self.matmul(v1, v2)
+            assert_equal(res, tgt1)
+            # no broadcast, we must make v1 into a 2d ndarray
+            res = self.matmul(v2, v1.reshape(1, -1))
+            assert_equal(res, tgt2)
+
+        # boolean type
+        vec = np.array([True, True], dtype='?')
+        res = self.matmul(vec, vec)
+        assert_equal(res, True)
+
+    def test_vector_matrix_values(self):
+        vec = np.array([1, 2])
+        mat1 = np.array([[1, 2], [3, 4]])
+        mat2 = np.stack([mat1]*2, axis=0)
+        tgt1 = np.array([7, 10])
+        tgt2 = np.stack([tgt1]*2, axis=0)
+        for dt in self.types[1:]:
+            v = vec.astype(dt)
+            m1 = mat1.astype(dt)
+            m2 = mat2.astype(dt)
+            res = self.matmul(v, m1)
+            assert_equal(res, tgt1)
+            res = self.matmul(v, m2)
+            assert_equal(res, tgt2)
+
+        # boolean type
+        vec = np.array([True, False])
+        mat1 = np.array([[True, False], [False, True]])
+        mat2 = np.stack([mat1]*2, axis=0)
+        tgt1 = np.array([True, False])
+        tgt2 = np.stack([tgt1]*2, axis=0)
+
+        res = self.matmul(vec, mat1)
+        assert_equal(res, tgt1)
+        res = self.matmul(vec, mat2)
+        assert_equal(res, tgt2)
+
+    def test_matrix_vector_values(self):
+        vec = np.array([1, 2])
+        mat1 = np.array([[1, 2], [3, 4]])
+        mat2 = np.stack([mat1]*2, axis=0)
+        tgt1 = np.array([5, 11])
+        tgt2 = np.stack([tgt1]*2, axis=0)
+        for dt in self.types[1:]:
+            v = vec.astype(dt)
+            m1 = mat1.astype(dt)
+            m2 = mat2.astype(dt)
+            res = self.matmul(m1, v)
+            assert_equal(res, tgt1)
+            res = self.matmul(m2, v)
+            assert_equal(res, tgt2)
+
+        # boolean type
+        vec = np.array([True, False])
+        mat1 = np.array([[True, False], [False, True]])
+        mat2 = np.stack([mat1]*2, axis=0)
+        tgt1 = np.array([True, False])
+        tgt2 = np.stack([tgt1]*2, axis=0)
+
+        res = self.matmul(vec, mat1)
+        assert_equal(res, tgt1)
+        res = self.matmul(vec, mat2)
+        assert_equal(res, tgt2)
+
+    def test_matrix_matrix_values(self):
+        mat1 = np.array([[1, 2], [3, 4]])
+        mat2 = np.array([[1, 0], [1, 1]])
+        mat12 = np.stack([mat1, mat2], axis=0)
+        mat21 = np.stack([mat2, mat1], axis=0)
+        tgt11 = np.array([[7, 10], [15, 22]])
+        tgt12 = np.array([[3, 2], [7, 4]])
+        tgt21 = np.array([[1, 2], [4, 6]])
+        tgt12_21 = np.stack([tgt12, tgt21], axis=0)
+        tgt11_12 = np.stack((tgt11, tgt12), axis=0)
+        tgt11_21 = np.stack((tgt11, tgt21), axis=0)
+        for dt in self.types[1:]:
+            m1 = mat1.astype(dt)
+            m2 = mat2.astype(dt)
+            m12 = mat12.astype(dt)
+            m21 = mat21.astype(dt)
+
+            # matrix @ matrix
+            res = self.matmul(m1, m2)
+            assert_equal(res, tgt12)
+            res = self.matmul(m2, m1)
+            assert_equal(res, tgt21)
+
+            # stacked @ matrix
+            res = self.matmul(m12, m1)
+            assert_equal(res, tgt11_21)
+
+            # matrix @ stacked
+            res = self.matmul(m1, m12)
+            assert_equal(res, tgt11_12)
+
+            # stacked @ stacked
+            res = self.matmul(m12, m21)
+            assert_equal(res, tgt12_21)
+
+        # boolean type
+        m1 = np.array([[1, 1], [0, 0]], dtype=np.bool_)
+        m2 = np.array([[1, 0], [1, 1]], dtype=np.bool_)
+        m12 = np.stack([m1, m2], axis=0)
+        m21 = np.stack([m2, m1], axis=0)
+        tgt11 = m1
+        tgt12 = m1
+        tgt21 = np.array([[1, 1], [1, 1]], dtype=np.bool_)
+        tgt12_21 = np.stack([tgt12, tgt21], axis=0)
+        tgt11_12 = np.stack((tgt11, tgt12), axis=0)
+        tgt11_21 = np.stack((tgt11, tgt21), axis=0)
+
+        # matrix @ matrix
+        res = self.matmul(m1, m2)
+        assert_equal(res, tgt12)
+        res = self.matmul(m2, m1)
+        assert_equal(res, tgt21)
+
+        # stacked @ matrix
+        res = self.matmul(m12, m1)
+        assert_equal(res, tgt11_21)
+
+        # matrix @ stacked
+        res = self.matmul(m1, m12)
+        assert_equal(res, tgt11_12)
+
+        # stacked @ stacked
+        res = self.matmul(m12, m21)
+        assert_equal(res, tgt12_21)
+
+
+class TestMatmul(MatmulCommon):
+    matmul = np.matmul
+
+    def test_out_arg(self):
+        a = np.ones((5, 2), dtype=float)
+        b = np.array([[1, 3], [5, 7]], dtype=float)
+        tgt = np.dot(a, b)
+
+        # test as positional argument
+        msg = "out positional argument"
+        out = np.zeros((5, 2), dtype=float)
+        self.matmul(a, b, out)
+        assert_array_equal(out, tgt, err_msg=msg)
+
+        # test as keyword argument
+        msg = "out keyword argument"
+        out = np.zeros((5, 2), dtype=float)
+        self.matmul(a, b, out=out)
+        assert_array_equal(out, tgt, err_msg=msg)
+
+        # test out with not allowed type cast (safe casting)
+        msg = "Cannot cast ufunc .* output"
+        out = np.zeros((5, 2), dtype=np.int32)
+        assert_raises_regex(TypeError, msg, self.matmul, a, b, out=out)
+
+        # test out with type upcast to complex
+        out = np.zeros((5, 2), dtype=np.complex128)
+        c = self.matmul(a, b, out=out)
+        assert_(c is out)
+        with suppress_warnings() as sup:
+            sup.filter(np.ComplexWarning, '')
+            c = c.astype(tgt.dtype)
+        assert_array_equal(c, tgt)
+
+    def test_empty_out(self):
+        # Check that the output cannot be broadcast, so that it cannot be
+        # size zero when the outer dimensions (iterator size) has size zero.
+        arr = np.ones((0, 1, 1))
+        out = np.ones((1, 1, 1))
+        assert self.matmul(arr, arr).shape == (0, 1, 1)
+
+        with pytest.raises(ValueError, match=r"non-broadcastable"):
+            self.matmul(arr, arr, out=out)
+
+    def test_out_contiguous(self):
+        a = np.ones((5, 2), dtype=float)
+        b = np.array([[1, 3], [5, 7]], dtype=float)
+        v = np.array([1, 3], dtype=float)
+        tgt = np.dot(a, b)
+        tgt_mv = np.dot(a, v)
+
+        # test out non-contiguous
+        out = np.ones((5, 2, 2), dtype=float)
+        c = self.matmul(a, b, out=out[..., 0])
+        assert c.base is out
+        assert_array_equal(c, tgt)
+        c = self.matmul(a, v, out=out[:, 0, 0])
+        assert_array_equal(c, tgt_mv)
+        c = self.matmul(v, a.T, out=out[:, 0, 0])
+        assert_array_equal(c, tgt_mv)
+
+        # test out contiguous in only last dim
+        out = np.ones((10, 2), dtype=float)
+        c = self.matmul(a, b, out=out[::2, :])
+        assert_array_equal(c, tgt)
+
+        # test transposes of out, args
+        out = np.ones((5, 2), dtype=float)
+        c = self.matmul(b.T, a.T, out=out.T)
+        assert_array_equal(out, tgt)
+
+    m1 = np.arange(15.).reshape(5, 3)
+    m2 = np.arange(21.).reshape(3, 7)
+    m3 = np.arange(30.).reshape(5, 6)[:, ::2]  # non-contiguous
+    vc = np.arange(10.)
+    vr = np.arange(6.)
+    m0 = np.zeros((3, 0))
+    @pytest.mark.parametrize('args', (
+            # matrix-matrix
+            (m1, m2), (m2.T, m1.T), (m2.T.copy(), m1.T), (m2.T, m1.T.copy()),
+            # matrix-matrix-transpose, contiguous and non
+            (m1, m1.T), (m1.T, m1), (m1, m3.T), (m3, m1.T),
+            (m3, m3.T), (m3.T, m3),
+            # matrix-matrix non-contiguous
+            (m3, m2), (m2.T, m3.T), (m2.T.copy(), m3.T),
+            # vector-matrix, matrix-vector, contiguous
+            (m1, vr[:3]), (vc[:5], m1), (m1.T, vc[:5]), (vr[:3], m1.T),
+            # vector-matrix, matrix-vector, vector non-contiguous
+            (m1, vr[::2]), (vc[::2], m1), (m1.T, vc[::2]), (vr[::2], m1.T),
+            # vector-matrix, matrix-vector, matrix non-contiguous
+            (m3, vr[:3]), (vc[:5], m3), (m3.T, vc[:5]), (vr[:3], m3.T),
+            # vector-matrix, matrix-vector, both non-contiguous
+            (m3, vr[::2]), (vc[::2], m3), (m3.T, vc[::2]), (vr[::2], m3.T),
+            # size == 0
+            (m0, m0.T), (m0.T, m0), (m1, m0), (m0.T, m1.T),
+        ))
+    def test_dot_equivalent(self, args):
+        r1 = np.matmul(*args)
+        r2 = np.dot(*args)
+        assert_equal(r1, r2)
+
+        r3 = np.matmul(args[0].copy(), args[1].copy())
+        assert_equal(r1, r3)
+
+    def test_matmul_object(self):
+        import fractions
+
+        f = np.vectorize(fractions.Fraction)
+        def random_ints():
+            return np.random.randint(1, 1000, size=(10, 3, 3))
+        M1 = f(random_ints(), random_ints())
+        M2 = f(random_ints(), random_ints())
+
+        M3 = self.matmul(M1, M2)
+
+        [N1, N2, N3] = [a.astype(float) for a in [M1, M2, M3]]
+
+        assert_allclose(N3, self.matmul(N1, N2))
+
+    def test_matmul_object_type_scalar(self):
+        from fractions import Fraction as F
+        v = np.array([F(2,3), F(5,7)])
+        res = self.matmul(v, v)
+        assert_(type(res) is F)
+
+    def test_matmul_empty(self):
+        a = np.empty((3, 0), dtype=object)
+        b = np.empty((0, 3), dtype=object)
+        c = np.zeros((3, 3))
+        assert_array_equal(np.matmul(a, b), c)
+
+    def test_matmul_exception_multiply(self):
+        # test that matmul fails if `__mul__` is missing
+        class add_not_multiply():
+            def __add__(self, other):
+                return self
+        a = np.full((3,3), add_not_multiply())
+        with assert_raises(TypeError):
+            b = np.matmul(a, a)
+
+    def test_matmul_exception_add(self):
+        # test that matmul fails if `__add__` is missing
+        class multiply_not_add():
+            def __mul__(self, other):
+                return self
+        a = np.full((3,3), multiply_not_add())
+        with assert_raises(TypeError):
+            b = np.matmul(a, a)
+
+    def test_matmul_bool(self):
+        # gh-14439
+        a = np.array([[1, 0],[1, 1]], dtype=bool)
+        assert np.max(a.view(np.uint8)) == 1
+        b = np.matmul(a, a)
+        # matmul with boolean output should always be 0, 1
+        assert np.max(b.view(np.uint8)) == 1
+
+        rg = np.random.default_rng(np.random.PCG64(43))
+        d = rg.integers(2, size=4*5, dtype=np.int8)
+        d = d.reshape(4, 5) > 0
+        out1 = np.matmul(d, d.reshape(5, 4))
+        out2 = np.dot(d, d.reshape(5, 4))
+        assert_equal(out1, out2)
+
+        c = np.matmul(np.zeros((2, 0), dtype=bool), np.zeros(0, dtype=bool))
+        assert not np.any(c)
+
+
+class TestMatmulOperator(MatmulCommon):
+    import operator
+    matmul = operator.matmul
+
+    def test_array_priority_override(self):
+
+        class A:
+            __array_priority__ = 1000
+
+            def __matmul__(self, other):
+                return "A"
+
+            def __rmatmul__(self, other):
+                return "A"
+
+        a = A()
+        b = np.ones(2)
+        assert_equal(self.matmul(a, b), "A")
+        assert_equal(self.matmul(b, a), "A")
+
+    def test_matmul_raises(self):
+        assert_raises(TypeError, self.matmul, np.int8(5), np.int8(5))
+        assert_raises(TypeError, self.matmul, np.void(b'abc'), np.void(b'abc'))
+        assert_raises(TypeError, self.matmul, np.arange(10), np.void(b'abc'))
+
+
+class TestMatmulInplace:
+    DTYPES = {}
+    for i in MatmulCommon.types:
+        for j in MatmulCommon.types:
+            if np.can_cast(j, i):
+                DTYPES[f"{i}-{j}"] = (np.dtype(i), np.dtype(j))
+
+    @pytest.mark.parametrize("dtype1,dtype2", DTYPES.values(), ids=DTYPES)
+    def test_basic(self, dtype1: np.dtype, dtype2: np.dtype) -> None:
+        a = np.arange(10).reshape(5, 2).astype(dtype1)
+        a_id = id(a)
+        b = np.ones((2, 2), dtype=dtype2)
+
+        ref = a @ b
+        a @= b
+
+        assert id(a) == a_id
+        assert a.dtype == dtype1
+        assert a.shape == (5, 2)
+        if dtype1.kind in "fc":
+            np.testing.assert_allclose(a, ref)
+        else:
+            np.testing.assert_array_equal(a, ref)
+
+    SHAPES = {
+        "2d_large": ((10**5, 10), (10, 10)),
+        "3d_large": ((10**4, 10, 10), (1, 10, 10)),
+        "1d": ((3,), (3,)),
+        "2d_1d": ((3, 3), (3,)),
+        "1d_2d": ((3,), (3, 3)),
+        "2d_broadcast": ((3, 3), (3, 1)),
+        "2d_broadcast_reverse": ((1, 3), (3, 3)),
+        "3d_broadcast1": ((3, 3, 3), (1, 3, 1)),
+        "3d_broadcast2": ((3, 3, 3), (1, 3, 3)),
+        "3d_broadcast3": ((3, 3, 3), (3, 3, 1)),
+        "3d_broadcast_reverse1": ((1, 3, 3), (3, 3, 3)),
+        "3d_broadcast_reverse2": ((3, 1, 3), (3, 3, 3)),
+        "3d_broadcast_reverse3": ((1, 1, 3), (3, 3, 3)),
+    }
+
+    @pytest.mark.parametrize("a_shape,b_shape", SHAPES.values(), ids=SHAPES)
+    def test_shapes(self, a_shape: tuple[int, ...], b_shape: tuple[int, ...]):
+        a_size = np.prod(a_shape)
+        a = np.arange(a_size).reshape(a_shape).astype(np.float64)
+        a_id = id(a)
+
+        b_size = np.prod(b_shape)
+        b = np.arange(b_size).reshape(b_shape)
+
+        ref = a @ b
+        if ref.shape != a_shape:
+            with pytest.raises(ValueError):
+                a @= b
+            return
+        else:
+            a @= b
+
+        assert id(a) == a_id
+        assert a.dtype.type == np.float64
+        assert a.shape == a_shape
+        np.testing.assert_allclose(a, ref)
+
+
+def test_matmul_axes():
+    a = np.arange(3*4*5).reshape(3, 4, 5)
+    c = np.matmul(a, a, axes=[(-2, -1), (-1, -2), (1, 2)])
+    assert c.shape == (3, 4, 4)
+    d = np.matmul(a, a, axes=[(-2, -1), (-1, -2), (0, 1)])
+    assert d.shape == (4, 4, 3)
+    e = np.swapaxes(d, 0, 2)
+    assert_array_equal(e, c)
+    f = np.matmul(a, np.arange(3), axes=[(1, 0), (0), (0)])
+    assert f.shape == (4, 5)
+
+
+class TestInner:
+
+    def test_inner_type_mismatch(self):
+        c = 1.
+        A = np.array((1,1), dtype='i,i')
+
+        assert_raises(TypeError, np.inner, c, A)
+        assert_raises(TypeError, np.inner, A, c)
+
+    def test_inner_scalar_and_vector(self):
+        for dt in np.typecodes['AllInteger'] + np.typecodes['AllFloat'] + '?':
+            sca = np.array(3, dtype=dt)[()]
+            vec = np.array([1, 2], dtype=dt)
+            desired = np.array([3, 6], dtype=dt)
+            assert_equal(np.inner(vec, sca), desired)
+            assert_equal(np.inner(sca, vec), desired)
+
+    def test_vecself(self):
+        # Ticket 844.
+        # Inner product of a vector with itself segfaults or give
+        # meaningless result
+        a = np.zeros(shape=(1, 80), dtype=np.float64)
+        p = np.inner(a, a)
+        assert_almost_equal(p, 0, decimal=14)
+
+    def test_inner_product_with_various_contiguities(self):
+        # github issue 6532
+        for dt in np.typecodes['AllInteger'] + np.typecodes['AllFloat'] + '?':
+            # check an inner product involving a matrix transpose
+            A = np.array([[1, 2], [3, 4]], dtype=dt)
+            B = np.array([[1, 3], [2, 4]], dtype=dt)
+            C = np.array([1, 1], dtype=dt)
+            desired = np.array([4, 6], dtype=dt)
+            assert_equal(np.inner(A.T, C), desired)
+            assert_equal(np.inner(C, A.T), desired)
+            assert_equal(np.inner(B, C), desired)
+            assert_equal(np.inner(C, B), desired)
+            # check a matrix product
+            desired = np.array([[7, 10], [15, 22]], dtype=dt)
+            assert_equal(np.inner(A, B), desired)
+            # check the syrk vs. gemm paths
+            desired = np.array([[5, 11], [11, 25]], dtype=dt)
+            assert_equal(np.inner(A, A), desired)
+            assert_equal(np.inner(A, A.copy()), desired)
+            # check an inner product involving an aliased and reversed view
+            a = np.arange(5).astype(dt)
+            b = a[::-1]
+            desired = np.array(10, dtype=dt).item()
+            assert_equal(np.inner(b, a), desired)
+
+    def test_3d_tensor(self):
+        for dt in np.typecodes['AllInteger'] + np.typecodes['AllFloat'] + '?':
+            a = np.arange(24).reshape(2,3,4).astype(dt)
+            b = np.arange(24, 48).reshape(2,3,4).astype(dt)
+            desired = np.array(
+                [[[[ 158,  182,  206],
+                   [ 230,  254,  278]],
+
+                  [[ 566,  654,  742],
+                   [ 830,  918, 1006]],
+
+                  [[ 974, 1126, 1278],
+                   [1430, 1582, 1734]]],
+
+                 [[[1382, 1598, 1814],
+                   [2030, 2246, 2462]],
+
+                  [[1790, 2070, 2350],
+                   [2630, 2910, 3190]],
+
+                  [[2198, 2542, 2886],
+                   [3230, 3574, 3918]]]]
+            ).astype(dt)
+            assert_equal(np.inner(a, b), desired)
+            assert_equal(np.inner(b, a).transpose(2,3,0,1), desired)
+
+
+class TestChoose:
+    def setup_method(self):
+        self.x = 2*np.ones((3,), dtype=int)
+        self.y = 3*np.ones((3,), dtype=int)
+        self.x2 = 2*np.ones((2, 3), dtype=int)
+        self.y2 = 3*np.ones((2, 3), dtype=int)
+        self.ind = [0, 0, 1]
+
+    def test_basic(self):
+        A = np.choose(self.ind, (self.x, self.y))
+        assert_equal(A, [2, 2, 3])
+
+    def test_broadcast1(self):
+        A = np.choose(self.ind, (self.x2, self.y2))
+        assert_equal(A, [[2, 2, 3], [2, 2, 3]])
+
+    def test_broadcast2(self):
+        A = np.choose(self.ind, (self.x, self.y2))
+        assert_equal(A, [[2, 2, 3], [2, 2, 3]])
+
+    @pytest.mark.parametrize("ops",
+        [(1000, np.array([1], dtype=np.uint8)),
+         (-1, np.array([1], dtype=np.uint8)),
+         (1., np.float32(3)),
+         (1., np.array([3], dtype=np.float32))],)
+    def test_output_dtype(self, ops):
+        expected_dt = np.result_type(*ops)
+        assert(np.choose([0], ops).dtype == expected_dt)
+
+
+class TestRepeat:
+    def setup_method(self):
+        self.m = np.array([1, 2, 3, 4, 5, 6])
+        self.m_rect = self.m.reshape((2, 3))
+
+    def test_basic(self):
+        A = np.repeat(self.m, [1, 3, 2, 1, 1, 2])
+        assert_equal(A, [1, 2, 2, 2, 3,
+                         3, 4, 5, 6, 6])
+
+    def test_broadcast1(self):
+        A = np.repeat(self.m, 2)
+        assert_equal(A, [1, 1, 2, 2, 3, 3,
+                         4, 4, 5, 5, 6, 6])
+
+    def test_axis_spec(self):
+        A = np.repeat(self.m_rect, [2, 1], axis=0)
+        assert_equal(A, [[1, 2, 3],
+                         [1, 2, 3],
+                         [4, 5, 6]])
+
+        A = np.repeat(self.m_rect, [1, 3, 2], axis=1)
+        assert_equal(A, [[1, 2, 2, 2, 3, 3],
+                         [4, 5, 5, 5, 6, 6]])
+
+    def test_broadcast2(self):
+        A = np.repeat(self.m_rect, 2, axis=0)
+        assert_equal(A, [[1, 2, 3],
+                         [1, 2, 3],
+                         [4, 5, 6],
+                         [4, 5, 6]])
+
+        A = np.repeat(self.m_rect, 2, axis=1)
+        assert_equal(A, [[1, 1, 2, 2, 3, 3],
+                         [4, 4, 5, 5, 6, 6]])
+
+
+# TODO: test for multidimensional
+NEIGH_MODE = {'zero': 0, 'one': 1, 'constant': 2, 'circular': 3, 'mirror': 4}
+
+
+@pytest.mark.parametrize('dt', [float, Decimal], ids=['float', 'object'])
+class TestNeighborhoodIter:
+    # Simple, 2d tests
+    def test_simple2d(self, dt):
+        # Test zero and one padding for simple data type
+        x = np.array([[0, 1], [2, 3]], dtype=dt)
+        r = [np.array([[0, 0, 0], [0, 0, 1]], dtype=dt),
+             np.array([[0, 0, 0], [0, 1, 0]], dtype=dt),
+             np.array([[0, 0, 1], [0, 2, 3]], dtype=dt),
+             np.array([[0, 1, 0], [2, 3, 0]], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 0, -1, 1], x[0], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        r = [np.array([[1, 1, 1], [1, 0, 1]], dtype=dt),
+             np.array([[1, 1, 1], [0, 1, 1]], dtype=dt),
+             np.array([[1, 0, 1], [1, 2, 3]], dtype=dt),
+             np.array([[0, 1, 1], [2, 3, 1]], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 0, -1, 1], x[0], NEIGH_MODE['one'])
+        assert_array_equal(l, r)
+
+        r = [np.array([[4, 4, 4], [4, 0, 1]], dtype=dt),
+             np.array([[4, 4, 4], [0, 1, 4]], dtype=dt),
+             np.array([[4, 0, 1], [4, 2, 3]], dtype=dt),
+             np.array([[0, 1, 4], [2, 3, 4]], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 0, -1, 1], 4, NEIGH_MODE['constant'])
+        assert_array_equal(l, r)
+
+        # Test with start in the middle
+        r = [np.array([[4, 0, 1], [4, 2, 3]], dtype=dt),
+             np.array([[0, 1, 4], [2, 3, 4]], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 0, -1, 1], 4, NEIGH_MODE['constant'], 2)
+        assert_array_equal(l, r)
+
+    def test_mirror2d(self, dt):
+        x = np.array([[0, 1], [2, 3]], dtype=dt)
+        r = [np.array([[0, 0, 1], [0, 0, 1]], dtype=dt),
+             np.array([[0, 1, 1], [0, 1, 1]], dtype=dt),
+             np.array([[0, 0, 1], [2, 2, 3]], dtype=dt),
+             np.array([[0, 1, 1], [2, 3, 3]], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 0, -1, 1], x[0], NEIGH_MODE['mirror'])
+        assert_array_equal(l, r)
+
+    # Simple, 1d tests
+    def test_simple(self, dt):
+        # Test padding with constant values
+        x = np.linspace(1, 5, 5).astype(dt)
+        r = [[0, 1, 2], [1, 2, 3], [2, 3, 4], [3, 4, 5], [4, 5, 0]]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 1], x[0], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        r = [[1, 1, 2], [1, 2, 3], [2, 3, 4], [3, 4, 5], [4, 5, 1]]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 1], x[0], NEIGH_MODE['one'])
+        assert_array_equal(l, r)
+
+        r = [[x[4], 1, 2], [1, 2, 3], [2, 3, 4], [3, 4, 5], [4, 5, x[4]]]
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-1, 1], x[4], NEIGH_MODE['constant'])
+        assert_array_equal(l, r)
+
+    # Test mirror modes
+    def test_mirror(self, dt):
+        x = np.linspace(1, 5, 5).astype(dt)
+        r = np.array([[2, 1, 1, 2, 3], [1, 1, 2, 3, 4], [1, 2, 3, 4, 5],
+                [2, 3, 4, 5, 5], [3, 4, 5, 5, 4]], dtype=dt)
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-2, 2], x[1], NEIGH_MODE['mirror'])
+        assert_([i.dtype == dt for i in l])
+        assert_array_equal(l, r)
+
+    # Circular mode
+    def test_circular(self, dt):
+        x = np.linspace(1, 5, 5).astype(dt)
+        r = np.array([[4, 5, 1, 2, 3], [5, 1, 2, 3, 4], [1, 2, 3, 4, 5],
+                [2, 3, 4, 5, 1], [3, 4, 5, 1, 2]], dtype=dt)
+        l = _multiarray_tests.test_neighborhood_iterator(
+                x, [-2, 2], x[0], NEIGH_MODE['circular'])
+        assert_array_equal(l, r)
+
+
+# Test stacking neighborhood iterators
+class TestStackedNeighborhoodIter:
+    # Simple, 1d test: stacking 2 constant-padded neigh iterators
+    def test_simple_const(self):
+        dt = np.float64
+        # Test zero and one padding for simple data type
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([0], dtype=dt),
+             np.array([0], dtype=dt),
+             np.array([1], dtype=dt),
+             np.array([2], dtype=dt),
+             np.array([3], dtype=dt),
+             np.array([0], dtype=dt),
+             np.array([0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-2, 4], NEIGH_MODE['zero'], [0, 0], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        r = [np.array([1, 0, 1], dtype=dt),
+             np.array([0, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 0], dtype=dt),
+             np.array([3, 0, 1], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [-1, 1], NEIGH_MODE['one'])
+        assert_array_equal(l, r)
+
+    # 2nd simple, 1d test: stacking 2 neigh iterators, mixing const padding and
+    # mirror padding
+    def test_simple_mirror(self):
+        dt = np.float64
+        # Stacking zero on top of mirror
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([0, 1, 1], dtype=dt),
+             np.array([1, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 3], dtype=dt),
+             np.array([3, 3, 0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['mirror'], [-1, 1], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([1, 0, 0], dtype=dt),
+             np.array([0, 0, 1], dtype=dt),
+             np.array([0, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [-2, 0], NEIGH_MODE['mirror'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero: 2nd
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([0, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 0], dtype=dt),
+             np.array([3, 0, 0], dtype=dt),
+             np.array([0, 0, 3], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [0, 2], NEIGH_MODE['mirror'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero: 3rd
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([1, 0, 0, 1, 2], dtype=dt),
+             np.array([0, 0, 1, 2, 3], dtype=dt),
+             np.array([0, 1, 2, 3, 0], dtype=dt),
+             np.array([1, 2, 3, 0, 0], dtype=dt),
+             np.array([2, 3, 0, 0, 3], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [-2, 2], NEIGH_MODE['mirror'])
+        assert_array_equal(l, r)
+
+    # 3rd simple, 1d test: stacking 2 neigh iterators, mixing const padding and
+    # circular padding
+    def test_simple_circular(self):
+        dt = np.float64
+        # Stacking zero on top of mirror
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([0, 3, 1], dtype=dt),
+             np.array([3, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 1], dtype=dt),
+             np.array([3, 1, 0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['circular'], [-1, 1], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([3, 0, 0], dtype=dt),
+             np.array([0, 0, 1], dtype=dt),
+             np.array([0, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [-2, 0], NEIGH_MODE['circular'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero: 2nd
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([0, 1, 2], dtype=dt),
+             np.array([1, 2, 3], dtype=dt),
+             np.array([2, 3, 0], dtype=dt),
+             np.array([3, 0, 0], dtype=dt),
+             np.array([0, 0, 1], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [0, 2], NEIGH_MODE['circular'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero: 3rd
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([3, 0, 0, 1, 2], dtype=dt),
+             np.array([0, 0, 1, 2, 3], dtype=dt),
+             np.array([0, 1, 2, 3, 0], dtype=dt),
+             np.array([1, 2, 3, 0, 0], dtype=dt),
+             np.array([2, 3, 0, 0, 1], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [-1, 3], NEIGH_MODE['zero'], [-2, 2], NEIGH_MODE['circular'])
+        assert_array_equal(l, r)
+
+    # 4th simple, 1d test: stacking 2 neigh iterators, but with lower iterator
+    # being strictly within the array
+    def test_simple_strict_within(self):
+        dt = np.float64
+        # Stacking zero on top of zero, first neighborhood strictly inside the
+        # array
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([1, 2, 3, 0], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [1, 1], NEIGH_MODE['zero'], [-1, 2], NEIGH_MODE['zero'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero, first neighborhood strictly inside the
+        # array
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([1, 2, 3, 3], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [1, 1], NEIGH_MODE['zero'], [-1, 2], NEIGH_MODE['mirror'])
+        assert_array_equal(l, r)
+
+        # Stacking mirror on top of zero, first neighborhood strictly inside the
+        # array
+        x = np.array([1, 2, 3], dtype=dt)
+        r = [np.array([1, 2, 3, 1], dtype=dt)]
+        l = _multiarray_tests.test_neighborhood_iterator_oob(
+                x, [1, 1], NEIGH_MODE['zero'], [-1, 2], NEIGH_MODE['circular'])
+        assert_array_equal(l, r)
+
+class TestWarnings:
+
+    def test_complex_warning(self):
+        x = np.array([1, 2])
+        y = np.array([1-2j, 1+2j])
+
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", np.ComplexWarning)
+            assert_raises(np.ComplexWarning, x.__setitem__, slice(None), y)
+            assert_equal(x, [1, 2])
+
+
+class TestMinScalarType:
+
+    def test_usigned_shortshort(self):
+        dt = np.min_scalar_type(2**8-1)
+        wanted = np.dtype('uint8')
+        assert_equal(wanted, dt)
+
+    def test_usigned_short(self):
+        dt = np.min_scalar_type(2**16-1)
+        wanted = np.dtype('uint16')
+        assert_equal(wanted, dt)
+
+    def test_usigned_int(self):
+        dt = np.min_scalar_type(2**32-1)
+        wanted = np.dtype('uint32')
+        assert_equal(wanted, dt)
+
+    def test_usigned_longlong(self):
+        dt = np.min_scalar_type(2**63-1)
+        wanted = np.dtype('uint64')
+        assert_equal(wanted, dt)
+
+    def test_object(self):
+        dt = np.min_scalar_type(2**64)
+        wanted = np.dtype('O')
+        assert_equal(wanted, dt)
+
+
+from numpy.core._internal import _dtype_from_pep3118
+
+
+class TestPEP3118Dtype:
+    def _check(self, spec, wanted):
+        dt = np.dtype(wanted)
+        actual = _dtype_from_pep3118(spec)
+        assert_equal(actual, dt,
+                     err_msg="spec %r != dtype %r" % (spec, wanted))
+
+    def test_native_padding(self):
+        align = np.dtype('i').alignment
+        for j in range(8):
+            if j == 0:
+                s = 'bi'
+            else:
+                s = 'b%dxi' % j
+            self._check('@'+s, {'f0': ('i1', 0),
+                                'f1': ('i', align*(1 + j//align))})
+            self._check('='+s, {'f0': ('i1', 0),
+                                'f1': ('i', 1+j)})
+
+    def test_native_padding_2(self):
+        # Native padding should work also for structs and sub-arrays
+        self._check('x3T{xi}', {'f0': (({'f0': ('i', 4)}, (3,)), 4)})
+        self._check('^x3T{xi}', {'f0': (({'f0': ('i', 1)}, (3,)), 1)})
+
+    def test_trailing_padding(self):
+        # Trailing padding should be included, *and*, the item size
+        # should match the alignment if in aligned mode
+        align = np.dtype('i').alignment
+        size = np.dtype('i').itemsize
+
+        def aligned(n):
+            return align*(1 + (n-1)//align)
+
+        base = dict(formats=['i'], names=['f0'])
+
+        self._check('ix',    dict(itemsize=aligned(size + 1), **base))
+        self._check('ixx',   dict(itemsize=aligned(size + 2), **base))
+        self._check('ixxx',  dict(itemsize=aligned(size + 3), **base))
+        self._check('ixxxx', dict(itemsize=aligned(size + 4), **base))
+        self._check('i7x',   dict(itemsize=aligned(size + 7), **base))
+
+        self._check('^ix',    dict(itemsize=size + 1, **base))
+        self._check('^ixx',   dict(itemsize=size + 2, **base))
+        self._check('^ixxx',  dict(itemsize=size + 3, **base))
+        self._check('^ixxxx', dict(itemsize=size + 4, **base))
+        self._check('^i7x',   dict(itemsize=size + 7, **base))
+
+    def test_native_padding_3(self):
+        dt = np.dtype(
+                [('a', 'b'), ('b', 'i'),
+                    ('sub', np.dtype('b,i')), ('c', 'i')],
+                align=True)
+        self._check("T{b:a:xxxi:b:T{b:f0:=i:f1:}:sub:xxxi:c:}", dt)
+
+        dt = np.dtype(
+                [('a', 'b'), ('b', 'i'), ('c', 'b'), ('d', 'b'),
+                    ('e', 'b'), ('sub', np.dtype('b,i', align=True))])
+        self._check("T{b:a:=i:b:b:c:b:d:b:e:T{b:f0:xxxi:f1:}:sub:}", dt)
+
+    def test_padding_with_array_inside_struct(self):
+        dt = np.dtype(
+                [('a', 'b'), ('b', 'i'), ('c', 'b', (3,)),
+                    ('d', 'i')],
+                align=True)
+        self._check("T{b:a:xxxi:b:3b:c:xi:d:}", dt)
+
+    def test_byteorder_inside_struct(self):
+        # The byte order after @T{=i} should be '=', not '@'.
+        # Check this by noting the absence of native alignment.
+        self._check('@T{^i}xi', {'f0': ({'f0': ('i', 0)}, 0),
+                                 'f1': ('i', 5)})
+
+    def test_intra_padding(self):
+        # Natively aligned sub-arrays may require some internal padding
+        align = np.dtype('i').alignment
+        size = np.dtype('i').itemsize
+
+        def aligned(n):
+            return (align*(1 + (n-1)//align))
+
+        self._check('(3)T{ix}', (dict(
+            names=['f0'],
+            formats=['i'],
+            offsets=[0],
+            itemsize=aligned(size + 1)
+        ), (3,)))
+
+    def test_char_vs_string(self):
+        dt = np.dtype('c')
+        self._check('c', dt)
+
+        dt = np.dtype([('f0', 'S1', (4,)), ('f1', 'S4')])
+        self._check('4c4s', dt)
+
+    def test_field_order(self):
+        # gh-9053 - previously, we relied on dictionary key order
+        self._check("(0)I:a:f:b:", [('a', 'I', (0,)), ('b', 'f')])
+        self._check("(0)I:b:f:a:", [('b', 'I', (0,)), ('a', 'f')])
+
+    def test_unnamed_fields(self):
+        self._check('ii',     [('f0', 'i'), ('f1', 'i')])
+        self._check('ii:f0:', [('f1', 'i'), ('f0', 'i')])
+
+        self._check('i', 'i')
+        self._check('i:f0:', [('f0', 'i')])
+
+
+class TestNewBufferProtocol:
+    """ Test PEP3118 buffers """
+
+    def _check_roundtrip(self, obj):
+        obj = np.asarray(obj)
+        x = memoryview(obj)
+        y = np.asarray(x)
+        y2 = np.array(x)
+        assert_(not y.flags.owndata)
+        assert_(y2.flags.owndata)
+
+        assert_equal(y.dtype, obj.dtype)
+        assert_equal(y.shape, obj.shape)
+        assert_array_equal(obj, y)
+
+        assert_equal(y2.dtype, obj.dtype)
+        assert_equal(y2.shape, obj.shape)
+        assert_array_equal(obj, y2)
+
+    def test_roundtrip(self):
+        x = np.array([1, 2, 3, 4, 5], dtype='i4')
+        self._check_roundtrip(x)
+
+        x = np.array([[1, 2], [3, 4]], dtype=np.float64)
+        self._check_roundtrip(x)
+
+        x = np.zeros((3, 3, 3), dtype=np.float32)[:, 0,:]
+        self._check_roundtrip(x)
+
+        dt = [('a', 'b'),
+              ('b', 'h'),
+              ('c', 'i'),
+              ('d', 'l'),
+              ('dx', 'q'),
+              ('e', 'B'),
+              ('f', 'H'),
+              ('g', 'I'),
+              ('h', 'L'),
+              ('hx', 'Q'),
+              ('i', np.single),
+              ('j', np.double),
+              ('k', np.longdouble),
+              ('ix', np.csingle),
+              ('jx', np.cdouble),
+              ('kx', np.clongdouble),
+              ('l', 'S4'),
+              ('m', 'U4'),
+              ('n', 'V3'),
+              ('o', '?'),
+              ('p', np.half),
+              ]
+        x = np.array(
+                [(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+                    b'aaaa', 'bbbb', b'xxx', True, 1.0)],
+                dtype=dt)
+        self._check_roundtrip(x)
+
+        x = np.array(([[1, 2], [3, 4]],), dtype=[('a', (int, (2, 2)))])
+        self._check_roundtrip(x)
+
+        x = np.array([1, 2, 3], dtype='>i2')
+        self._check_roundtrip(x)
+
+        x = np.array([1, 2, 3], dtype='<i2')
+        self._check_roundtrip(x)
+
+        x = np.array([1, 2, 3], dtype='>i4')
+        self._check_roundtrip(x)
+
+        x = np.array([1, 2, 3], dtype='<i4')
+        self._check_roundtrip(x)
+
+        # check long long can be represented as non-native
+        x = np.array([1, 2, 3], dtype='>q')
+        self._check_roundtrip(x)
+
+        # Native-only data types can be passed through the buffer interface
+        # only in native byte order
+        if sys.byteorder == 'little':
+            x = np.array([1, 2, 3], dtype='>g')
+            assert_raises(ValueError, self._check_roundtrip, x)
+            x = np.array([1, 2, 3], dtype='<g')
+            self._check_roundtrip(x)
+        else:
+            x = np.array([1, 2, 3], dtype='>g')
+            self._check_roundtrip(x)
+            x = np.array([1, 2, 3], dtype='<g')
+            assert_raises(ValueError, self._check_roundtrip, x)
+
+    def test_roundtrip_half(self):
+        half_list = [
+            1.0,
+            -2.0,
+            6.5504 * 10**4,  # (max half precision)
+            2**-14,  # ~= 6.10352 * 10**-5 (minimum positive normal)
+            2**-24,  # ~= 5.96046 * 10**-8 (minimum strictly positive subnormal)
+            0.0,
+            -0.0,
+            float('+inf'),
+            float('-inf'),
+            0.333251953125,  # ~= 1/3
+        ]
+
+        x = np.array(half_list, dtype='>e')
+        self._check_roundtrip(x)
+        x = np.array(half_list, dtype='<e')
+        self._check_roundtrip(x)
+
+    def test_roundtrip_single_types(self):
+        for typ in np.sctypeDict.values():
+            dtype = np.dtype(typ)
+
+            if dtype.char in 'Mm':
+                # datetimes cannot be used in buffers
+                continue
+            if dtype.char == 'V':
+                # skip void
+                continue
+
+            x = np.zeros(4, dtype=dtype)
+            self._check_roundtrip(x)
+
+            if dtype.char not in 'qQgG':
+                dt = dtype.newbyteorder('<')
+                x = np.zeros(4, dtype=dt)
+                self._check_roundtrip(x)
+
+                dt = dtype.newbyteorder('>')
+                x = np.zeros(4, dtype=dt)
+                self._check_roundtrip(x)
+
+    def test_roundtrip_scalar(self):
+        # Issue #4015.
+        self._check_roundtrip(0)
+
+    def test_invalid_buffer_format(self):
+        # datetime64 cannot be used fully in a buffer yet
+        # Should be fixed in the next Numpy major release
+        dt = np.dtype([('a', 'uint16'), ('b', 'M8[s]')])
+        a = np.empty(3, dt)
+        assert_raises((ValueError, BufferError), memoryview, a)
+        assert_raises((ValueError, BufferError), memoryview, np.array((3), 'M8[D]'))
+
+    def test_export_simple_1d(self):
+        x = np.array([1, 2, 3, 4, 5], dtype='i')
+        y = memoryview(x)
+        assert_equal(y.format, 'i')
+        assert_equal(y.shape, (5,))
+        assert_equal(y.ndim, 1)
+        assert_equal(y.strides, (4,))
+        assert_equal(y.suboffsets, ())
+        assert_equal(y.itemsize, 4)
+
+    def test_export_simple_nd(self):
+        x = np.array([[1, 2], [3, 4]], dtype=np.float64)
+        y = memoryview(x)
+        assert_equal(y.format, 'd')
+        assert_equal(y.shape, (2, 2))
+        assert_equal(y.ndim, 2)
+        assert_equal(y.strides, (16, 8))
+        assert_equal(y.suboffsets, ())
+        assert_equal(y.itemsize, 8)
+
+    def test_export_discontiguous(self):
+        x = np.zeros((3, 3, 3), dtype=np.float32)[:, 0,:]
+        y = memoryview(x)
+        assert_equal(y.format, 'f')
+        assert_equal(y.shape, (3, 3))
+        assert_equal(y.ndim, 2)
+        assert_equal(y.strides, (36, 4))
+        assert_equal(y.suboffsets, ())
+        assert_equal(y.itemsize, 4)
+
+    def test_export_record(self):
+        dt = [('a', 'b'),
+              ('b', 'h'),
+              ('c', 'i'),
+              ('d', 'l'),
+              ('dx', 'q'),
+              ('e', 'B'),
+              ('f', 'H'),
+              ('g', 'I'),
+              ('h', 'L'),
+              ('hx', 'Q'),
+              ('i', np.single),
+              ('j', np.double),
+              ('k', np.longdouble),
+              ('ix', np.csingle),
+              ('jx', np.cdouble),
+              ('kx', np.clongdouble),
+              ('l', 'S4'),
+              ('m', 'U4'),
+              ('n', 'V3'),
+              ('o', '?'),
+              ('p', np.half),
+              ]
+        x = np.array(
+                [(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+                    b'aaaa', 'bbbb', b'   ', True, 1.0)],
+                dtype=dt)
+        y = memoryview(x)
+        assert_equal(y.shape, (1,))
+        assert_equal(y.ndim, 1)
+        assert_equal(y.suboffsets, ())
+
+        sz = sum([np.dtype(b).itemsize for a, b in dt])
+        if np.dtype('l').itemsize == 4:
+            assert_equal(y.format, 'T{b:a:=h:b:i:c:l:d:q:dx:B:e:@H:f:=I:g:L:h:Q:hx:f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
+        else:
+            assert_equal(y.format, 'T{b:a:=h:b:i:c:q:d:q:dx:B:e:@H:f:=I:g:Q:h:Q:hx:f:i:d:j:^g:k:=Zf:ix:Zd:jx:^Zg:kx:4s:l:=4w:m:3x:n:?:o:@e:p:}')
+        # Cannot test if NPY_RELAXED_STRIDES_DEBUG changes the strides
+        if not (np.ones(1).strides[0] == np.iinfo(np.intp).max):
+            assert_equal(y.strides, (sz,))
+        assert_equal(y.itemsize, sz)
+
+    def test_export_subarray(self):
+        x = np.array(([[1, 2], [3, 4]],), dtype=[('a', ('i', (2, 2)))])
+        y = memoryview(x)
+        assert_equal(y.format, 'T{(2,2)i:a:}')
+        assert_equal(y.shape, ())
+        assert_equal(y.ndim, 0)
+        assert_equal(y.strides, ())
+        assert_equal(y.suboffsets, ())
+        assert_equal(y.itemsize, 16)
+
+    def test_export_endian(self):
+        x = np.array([1, 2, 3], dtype='>i')
+        y = memoryview(x)
+        if sys.byteorder == 'little':
+            assert_equal(y.format, '>i')
+        else:
+            assert_equal(y.format, 'i')
+
+        x = np.array([1, 2, 3], dtype='<i')
+        y = memoryview(x)
+        if sys.byteorder == 'little':
+            assert_equal(y.format, 'i')
+        else:
+            assert_equal(y.format, '<i')
+
+    def test_export_flags(self):
+        # Check SIMPLE flag, see also gh-3613 (exception should be BufferError)
+        assert_raises(ValueError,
+                      _multiarray_tests.get_buffer_info,
+                       np.arange(5)[::2], ('SIMPLE',))
+
+    @pytest.mark.parametrize(["obj", "error"], [
+            pytest.param(np.array([1, 2], dtype=rational), ValueError, id="array"),
+            pytest.param(rational(1, 2), TypeError, id="scalar")])
+    def test_export_and_pickle_user_dtype(self, obj, error):
+        # User dtypes should export successfully when FORMAT was not requested.
+        with pytest.raises(error):
+            _multiarray_tests.get_buffer_info(obj, ("STRIDED_RO", "FORMAT"))
+
+        _multiarray_tests.get_buffer_info(obj, ("STRIDED_RO",))
+
+        # This is currently also necessary to implement pickling:
+        pickle_obj = pickle.dumps(obj)
+        res = pickle.loads(pickle_obj)
+        assert_array_equal(res, obj)
+
+    def test_padding(self):
+        for j in range(8):
+            x = np.array([(1,), (2,)], dtype={'f0': (int, j)})
+            self._check_roundtrip(x)
+
+    def test_reference_leak(self):
+        if HAS_REFCOUNT:
+            count_1 = sys.getrefcount(np.core._internal)
+        a = np.zeros(4)
+        b = memoryview(a)
+        c = np.asarray(b)
+        if HAS_REFCOUNT:
+            count_2 = sys.getrefcount(np.core._internal)
+            assert_equal(count_1, count_2)
+        del c  # avoid pyflakes unused variable warning.
+
+    def test_padded_struct_array(self):
+        dt1 = np.dtype(
+                [('a', 'b'), ('b', 'i'), ('sub', np.dtype('b,i')), ('c', 'i')],
+                align=True)
+        x1 = np.arange(dt1.itemsize, dtype=np.int8).view(dt1)
+        self._check_roundtrip(x1)
+
+        dt2 = np.dtype(
+                [('a', 'b'), ('b', 'i'), ('c', 'b', (3,)), ('d', 'i')],
+                align=True)
+        x2 = np.arange(dt2.itemsize, dtype=np.int8).view(dt2)
+        self._check_roundtrip(x2)
+
+        dt3 = np.dtype(
+                [('a', 'b'), ('b', 'i'), ('c', 'b'), ('d', 'b'),
+                    ('e', 'b'), ('sub', np.dtype('b,i', align=True))])
+        x3 = np.arange(dt3.itemsize, dtype=np.int8).view(dt3)
+        self._check_roundtrip(x3)
+
+    @pytest.mark.valgrind_error(reason="leaks buffer info cache temporarily.")
+    def test_relaxed_strides(self, c=np.ones((1, 10, 10), dtype='i8')):
+        # Note: c defined as parameter so that it is persistent and leak
+        # checks will notice gh-16934 (buffer info cache leak).
+        c.strides = (-1, 80, 8)  # strides need to be fixed at export
+
+        assert_(memoryview(c).strides == (800, 80, 8))
+
+        # Writing C-contiguous data to a BytesIO buffer should work
+        fd = io.BytesIO()
+        fd.write(c.data)
+
+        fortran = c.T
+        assert_(memoryview(fortran).strides == (8, 80, 800))
+
+        arr = np.ones((1, 10))
+        if arr.flags.f_contiguous:
+            shape, strides = _multiarray_tests.get_buffer_info(
+                    arr, ['F_CONTIGUOUS'])
+            assert_(strides[0] == 8)
+            arr = np.ones((10, 1), order='F')
+            shape, strides = _multiarray_tests.get_buffer_info(
+                    arr, ['C_CONTIGUOUS'])
+            assert_(strides[-1] == 8)
+
+    @pytest.mark.valgrind_error(reason="leaks buffer info cache temporarily.")
+    @pytest.mark.skipif(not np.ones((10, 1), order="C").flags.f_contiguous,
+            reason="Test is unnecessary (but fails) without relaxed strides.")
+    def test_relaxed_strides_buffer_info_leak(self, arr=np.ones((1, 10))):
+        """Test that alternating export of C- and F-order buffers from
+        an array which is both C- and F-order when relaxed strides is
+        active works.
+        This test defines array in the signature to ensure leaking more
+        references every time the test is run (catching the leak with
+        pytest-leaks).
+        """
+        for i in range(10):
+            _, s = _multiarray_tests.get_buffer_info(arr, ['F_CONTIGUOUS'])
+            assert s == (8, 8)
+            _, s = _multiarray_tests.get_buffer_info(arr, ['C_CONTIGUOUS'])
+            assert s == (80, 8)
+
+    def test_out_of_order_fields(self):
+        dt = np.dtype(dict(
+            formats=['<i4', '<i4'],
+            names=['one', 'two'],
+            offsets=[4, 0],
+            itemsize=8
+        ))
+
+        # overlapping fields cannot be represented by PEP3118
+        arr = np.empty(1, dt)
+        with assert_raises(ValueError):
+            memoryview(arr)
+
+    def test_max_dims(self):
+        a = np.ones((1,) * 32)
+        self._check_roundtrip(a)
+
+    @pytest.mark.slow
+    def test_error_too_many_dims(self):
+        def make_ctype(shape, scalar_type):
+            t = scalar_type
+            for dim in shape[::-1]:
+                t = dim * t
+            return t
+
+        # construct a memoryview with 33 dimensions
+        c_u8_33d = make_ctype((1,)*33, ctypes.c_uint8)
+        m = memoryview(c_u8_33d())
+        assert_equal(m.ndim, 33)
+
+        assert_raises_regex(
+            RuntimeError, "ndim",
+            np.array, m)
+
+        # The above seems to create some deep cycles, clean them up for
+        # easier reference count debugging:
+        del c_u8_33d, m
+        for i in range(33):
+            if gc.collect() == 0:
+                break
+
+    def test_error_pointer_type(self):
+        # gh-6741
+        m = memoryview(ctypes.pointer(ctypes.c_uint8()))
+        assert_('&' in m.format)
+
+        assert_raises_regex(
+            ValueError, "format string",
+            np.array, m)
+
+    def test_error_message_unsupported(self):
+        # wchar has no corresponding numpy type - if this changes in future, we
+        # need a better way to construct an invalid memoryview format.
+        t = ctypes.c_wchar * 4
+        with assert_raises(ValueError) as cm:
+            np.array(t())
+
+        exc = cm.exception
+        with assert_raises_regex(
+            NotImplementedError,
+            r"Unrepresentable .* 'u' \(UCS-2 strings\)"
+        ):
+            raise exc.__cause__
+
+    def test_ctypes_integer_via_memoryview(self):
+        # gh-11150, due to bpo-10746
+        for c_integer in {ctypes.c_int, ctypes.c_long, ctypes.c_longlong}:
+            value = c_integer(42)
+            with warnings.catch_warnings(record=True):
+                warnings.filterwarnings('always', r'.*\bctypes\b', RuntimeWarning)
+                np.asarray(value)
+
+    def test_ctypes_struct_via_memoryview(self):
+        # gh-10528
+        class foo(ctypes.Structure):
+            _fields_ = [('a', ctypes.c_uint8), ('b', ctypes.c_uint32)]
+        f = foo(a=1, b=2)
+
+        with warnings.catch_warnings(record=True):
+            warnings.filterwarnings('always', r'.*\bctypes\b', RuntimeWarning)
+            arr = np.asarray(f)
+
+        assert_equal(arr['a'], 1)
+        assert_equal(arr['b'], 2)
+        f.a = 3
+        assert_equal(arr['a'], 3)
+
+    @pytest.mark.parametrize("obj", [np.ones(3), np.ones(1, dtype="i,i")[()]])
+    def test_error_if_stored_buffer_info_is_corrupted(self, obj):
+        """
+        If a user extends a NumPy array before 1.20 and then runs it
+        on NumPy 1.20+. A C-subclassed array might in theory modify
+        the new buffer-info field. This checks that an error is raised
+        if this happens (for buffer export), an error is written on delete.
+        This is a sanity check to help users transition to safe code, it
+        may be deleted at any point.
+        """
+        # corrupt buffer info:
+        _multiarray_tests.corrupt_or_fix_bufferinfo(obj)
+        name = type(obj)
+        with pytest.raises(RuntimeError,
+                    match=f".*{name} appears to be C subclassed"):
+            memoryview(obj)
+        # Fix buffer info again before we delete (or we lose the memory)
+        _multiarray_tests.corrupt_or_fix_bufferinfo(obj)
+
+    def test_no_suboffsets(self):
+        try:
+            import _testbuffer
+        except ImportError:
+            raise pytest.skip("_testbuffer is not available")
+
+        for shape in [(2, 3), (2, 3, 4)]:
+            data = list(range(np.prod(shape)))
+            buffer = _testbuffer.ndarray(data, shape, format='i',
+                                         flags=_testbuffer.ND_PIL)
+            msg = "NumPy currently does not support.*suboffsets"
+            with pytest.raises(BufferError, match=msg):
+                np.asarray(buffer)
+            with pytest.raises(BufferError, match=msg):
+                np.asarray([buffer])
+
+            # Also check (unrelated and more limited but similar) frombuffer:
+            with pytest.raises(BufferError):
+                np.frombuffer(buffer)
+
+
+class TestArrayCreationCopyArgument(object):
+
+    class RaiseOnBool:
+
+        def __bool__(self):
+            raise ValueError
+
+    true_vals = [True, np._CopyMode.ALWAYS, np.True_]
+    false_vals = [False, np._CopyMode.IF_NEEDED, np.False_]
+
+    def test_scalars(self):
+        # Test both numpy and python scalars
+        for dtype in np.typecodes["All"]:
+            arr = np.zeros((), dtype=dtype)
+            scalar = arr[()]
+            pyscalar = arr.item(0)
+
+            # Test never-copy raises error:
+            assert_raises(ValueError, np.array, scalar,
+                            copy=np._CopyMode.NEVER)
+            assert_raises(ValueError, np.array, pyscalar,
+                            copy=np._CopyMode.NEVER)
+            assert_raises(ValueError, np.array, pyscalar,
+                            copy=self.RaiseOnBool())
+            assert_raises(ValueError, _multiarray_tests.npy_ensurenocopy,
+                            [1])
+            # Casting with a dtype (to unsigned integers) can be special:
+            with pytest.raises(ValueError):
+                np.array(pyscalar, dtype=np.int64, copy=np._CopyMode.NEVER)
+
+    def test_compatible_cast(self):
+
+        # Some types are compatible even though they are different, no
+        # copy is necessary for them. This is mostly true for some integers
+        def int_types(byteswap=False):
+            int_types = (np.typecodes["Integer"] +
+                         np.typecodes["UnsignedInteger"])
+            for int_type in int_types:
+                yield np.dtype(int_type)
+                if byteswap:
+                    yield np.dtype(int_type).newbyteorder()
+
+        for int1 in int_types():
+            for int2 in int_types(True):
+                arr = np.arange(10, dtype=int1)
+
+                for copy in self.true_vals:
+                    res = np.array(arr, copy=copy, dtype=int2)
+                    assert res is not arr and res.flags.owndata
+                    assert_array_equal(res, arr)
+
+                if int1 == int2:
+                    # Casting is not necessary, base check is sufficient here
+                    for copy in self.false_vals:
+                        res = np.array(arr, copy=copy, dtype=int2)
+                        assert res is arr or res.base is arr
+
+                    res = np.array(arr,
+                                   copy=np._CopyMode.NEVER,
+                                   dtype=int2)
+                    assert res is arr or res.base is arr
+
+                else:
+                    # Casting is necessary, assert copy works:
+                    for copy in self.false_vals:
+                        res = np.array(arr, copy=copy, dtype=int2)
+                        assert res is not arr and res.flags.owndata
+                        assert_array_equal(res, arr)
+
+                    assert_raises(ValueError, np.array,
+                                  arr, copy=np._CopyMode.NEVER,
+                                  dtype=int2)
+                    assert_raises(ValueError, np.array,
+                                  arr, copy=None,
+                                  dtype=int2)
+
+    def test_buffer_interface(self):
+
+        # Buffer interface gives direct memory access (no copy)
+        arr = np.arange(10)
+        view = memoryview(arr)
+
+        # Checking bases is a bit tricky since numpy creates another
+        # memoryview, so use may_share_memory.
+        for copy in self.true_vals:
+            res = np.array(view, copy=copy)
+            assert not np.may_share_memory(arr, res)
+        for copy in self.false_vals:
+            res = np.array(view, copy=copy)
+            assert np.may_share_memory(arr, res)
+        res = np.array(view, copy=np._CopyMode.NEVER)
+        assert np.may_share_memory(arr, res)
+
+    def test_array_interfaces(self):
+        # Array interface gives direct memory access (much like a memoryview)
+        base_arr = np.arange(10)
+
+        class ArrayLike:
+            __array_interface__ = base_arr.__array_interface__
+
+        arr = ArrayLike()
+
+        for copy, val in [(True, None), (np._CopyMode.ALWAYS, None),
+                          (False, arr), (np._CopyMode.IF_NEEDED, arr),
+                          (np._CopyMode.NEVER, arr)]:
+            res = np.array(arr, copy=copy)
+            assert res.base is val
+
+    def test___array__(self):
+        base_arr = np.arange(10)
+
+        class ArrayLike:
+            def __array__(self):
+                # __array__ should return a copy, numpy cannot know this
+                # however.
+                return base_arr
+
+        arr = ArrayLike()
+
+        for copy in self.true_vals:
+            res = np.array(arr, copy=copy)
+            assert_array_equal(res, base_arr)
+            # An additional copy is currently forced by numpy in this case,
+            # you could argue, numpy does not trust the ArrayLike. This
+            # may be open for change:
+            assert res is not base_arr
+
+        for copy in self.false_vals:
+            res = np.array(arr, copy=False)
+            assert_array_equal(res, base_arr)
+            assert res is base_arr  # numpy trusts the ArrayLike
+
+        with pytest.raises(ValueError):
+            np.array(arr, copy=np._CopyMode.NEVER)
+
+    @pytest.mark.parametrize(
+            "arr", [np.ones(()), np.arange(81).reshape((9, 9))])
+    @pytest.mark.parametrize("order1", ["C", "F", None])
+    @pytest.mark.parametrize("order2", ["C", "F", "A", "K"])
+    def test_order_mismatch(self, arr, order1, order2):
+        # The order is the main (python side) reason that can cause
+        # a never-copy to fail.
+        # Prepare C-order, F-order and non-contiguous arrays:
+        arr = arr.copy(order1)
+        if order1 == "C":
+            assert arr.flags.c_contiguous
+        elif order1 == "F":
+            assert arr.flags.f_contiguous
+        elif arr.ndim != 0:
+            # Make array non-contiguous
+            arr = arr[::2, ::2]
+            assert not arr.flags.forc
+
+        # Whether a copy is necessary depends on the order of arr:
+        if order2 == "C":
+            no_copy_necessary = arr.flags.c_contiguous
+        elif order2 == "F":
+            no_copy_necessary = arr.flags.f_contiguous
+        else:
+            # Keeporder and Anyorder are OK with non-contiguous output.
+            # This is not consistent with the `astype` behaviour which
+            # enforces contiguity for "A". It is probably historic from when
+            # "K" did not exist.
+            no_copy_necessary = True
+
+        # Test it for both the array and a memoryview
+        for view in [arr, memoryview(arr)]:
+            for copy in self.true_vals:
+                res = np.array(view, copy=copy, order=order2)
+                assert res is not arr and res.flags.owndata
+                assert_array_equal(arr, res)
+
+            if no_copy_necessary:
+                for copy in self.false_vals:
+                    res = np.array(view, copy=copy, order=order2)
+                    # res.base.obj refers to the memoryview
+                    if not IS_PYPY:
+                        assert res is arr or res.base.obj is arr
+
+                res = np.array(view, copy=np._CopyMode.NEVER,
+                               order=order2)
+                if not IS_PYPY:
+                    assert res is arr or res.base.obj is arr
+            else:
+                for copy in self.false_vals:
+                    res = np.array(arr, copy=copy, order=order2)
+                    assert_array_equal(arr, res)
+                assert_raises(ValueError, np.array,
+                              view, copy=np._CopyMode.NEVER,
+                              order=order2)
+                assert_raises(ValueError, np.array,
+                              view, copy=None,
+                              order=order2)
+
+    def test_striding_not_ok(self):
+        arr = np.array([[1, 2, 4], [3, 4, 5]])
+        assert_raises(ValueError, np.array,
+                      arr.T, copy=np._CopyMode.NEVER,
+                      order='C')
+        assert_raises(ValueError, np.array,
+                      arr.T, copy=np._CopyMode.NEVER,
+                      order='C', dtype=np.int64)
+        assert_raises(ValueError, np.array,
+                      arr, copy=np._CopyMode.NEVER,
+                      order='F')
+        assert_raises(ValueError, np.array,
+                      arr, copy=np._CopyMode.NEVER,
+                      order='F', dtype=np.int64)
+
+
+class TestArrayAttributeDeletion:
+
+    def test_multiarray_writable_attributes_deletion(self):
+        # ticket #2046, should not seqfault, raise AttributeError
+        a = np.ones(2)
+        attr = ['shape', 'strides', 'data', 'dtype', 'real', 'imag', 'flat']
+        with suppress_warnings() as sup:
+            sup.filter(DeprecationWarning, "Assigning the 'data' attribute")
+            for s in attr:
+                assert_raises(AttributeError, delattr, a, s)
+
+    def test_multiarray_not_writable_attributes_deletion(self):
+        a = np.ones(2)
+        attr = ["ndim", "flags", "itemsize", "size", "nbytes", "base",
+                "ctypes", "T", "__array_interface__", "__array_struct__",
+                "__array_priority__", "__array_finalize__"]
+        for s in attr:
+            assert_raises(AttributeError, delattr, a, s)
+
+    def test_multiarray_flags_writable_attribute_deletion(self):
+        a = np.ones(2).flags
+        attr = ['writebackifcopy', 'updateifcopy', 'aligned', 'writeable']
+        for s in attr:
+            assert_raises(AttributeError, delattr, a, s)
+
+    def test_multiarray_flags_not_writable_attribute_deletion(self):
+        a = np.ones(2).flags
+        attr = ["contiguous", "c_contiguous", "f_contiguous", "fortran",
+                "owndata", "fnc", "forc", "behaved", "carray", "farray",
+                "num"]
+        for s in attr:
+            assert_raises(AttributeError, delattr, a, s)
+
+
+class TestArrayInterface():
+    class Foo:
+        def __init__(self, value):
+            self.value = value
+            self.iface = {'typestr': 'f8'}
+
+        def __float__(self):
+            return float(self.value)
+
+        @property
+        def __array_interface__(self):
+            return self.iface
+
+
+    f = Foo(0.5)
+
+    @pytest.mark.parametrize('val, iface, expected', [
+        (f, {}, 0.5),
+        ([f], {}, [0.5]),
+        ([f, f], {}, [0.5, 0.5]),
+        (f, {'shape': ()}, 0.5),
+        (f, {'shape': None}, TypeError),
+        (f, {'shape': (1, 1)}, [[0.5]]),
+        (f, {'shape': (2,)}, ValueError),
+        (f, {'strides': ()}, 0.5),
+        (f, {'strides': (2,)}, ValueError),
+        (f, {'strides': 16}, TypeError),
+        ])
+    def test_scalar_interface(self, val, iface, expected):
+        # Test scalar coercion within the array interface
+        self.f.iface = {'typestr': 'f8'}
+        self.f.iface.update(iface)
+        if HAS_REFCOUNT:
+            pre_cnt = sys.getrefcount(np.dtype('f8'))
+        if isinstance(expected, type):
+            assert_raises(expected, np.array, val)
+        else:
+            result = np.array(val)
+            assert_equal(np.array(val), expected)
+            assert result.dtype == 'f8'
+            del result
+        if HAS_REFCOUNT:
+            post_cnt = sys.getrefcount(np.dtype('f8'))
+            assert_equal(pre_cnt, post_cnt)
+
+def test_interface_no_shape():
+    class ArrayLike:
+        array = np.array(1)
+        __array_interface__ = array.__array_interface__
+    assert_equal(np.array(ArrayLike()), 1)
+
+
+def test_array_interface_itemsize():
+    # See gh-6361
+    my_dtype = np.dtype({'names': ['A', 'B'], 'formats': ['f4', 'f4'],
+                         'offsets': [0, 8], 'itemsize': 16})
+    a = np.ones(10, dtype=my_dtype)
+    descr_t = np.dtype(a.__array_interface__['descr'])
+    typestr_t = np.dtype(a.__array_interface__['typestr'])
+    assert_equal(descr_t.itemsize, typestr_t.itemsize)
+
+
+def test_array_interface_empty_shape():
+    # See gh-7994
+    arr = np.array([1, 2, 3])
+    interface1 = dict(arr.__array_interface__)
+    interface1['shape'] = ()
+
+    class DummyArray1:
+        __array_interface__ = interface1
+
+    # NOTE: Because Py2 str/Py3 bytes supports the buffer interface, setting
+    # the interface data to bytes would invoke the bug this tests for, that
+    # __array_interface__ with shape=() is not allowed if the data is an object
+    # exposing the buffer interface
+    interface2 = dict(interface1)
+    interface2['data'] = arr[0].tobytes()
+
+    class DummyArray2:
+        __array_interface__ = interface2
+
+    arr1 = np.asarray(DummyArray1())
+    arr2 = np.asarray(DummyArray2())
+    arr3 = arr[:1].reshape(())
+    assert_equal(arr1, arr2)
+    assert_equal(arr1, arr3)
+
+def test_array_interface_offset():
+    arr = np.array([1, 2, 3], dtype='int32')
+    interface = dict(arr.__array_interface__)
+    interface['data'] = memoryview(arr)
+    interface['shape'] = (2,)
+    interface['offset'] = 4
+
+
+    class DummyArray:
+        __array_interface__ = interface
+
+    arr1 = np.asarray(DummyArray())
+    assert_equal(arr1, arr[1:])
+
+def test_array_interface_unicode_typestr():
+    arr = np.array([1, 2, 3], dtype='int32')
+    interface = dict(arr.__array_interface__)
+    interface['typestr'] = '\N{check mark}'
+
+    class DummyArray:
+        __array_interface__ = interface
+
+    # should not be UnicodeEncodeError
+    with pytest.raises(TypeError):
+        np.asarray(DummyArray())
+
+def test_flat_element_deletion():
+    it = np.ones(3).flat
+    try:
+        del it[1]
+        del it[1:2]
+    except TypeError:
+        pass
+    except Exception:
+        raise AssertionError
+
+
+def test_scalar_element_deletion():
+    a = np.zeros(2, dtype=[('x', 'int'), ('y', 'int')])
+    assert_raises(ValueError, a[0].__delitem__, 'x')
+
+
+class TestMapIter:
+    def test_mapiter(self):
+        # The actual tests are within the C code in
+        # multiarray/_multiarray_tests.c.src
+
+        a = np.arange(12).reshape((3, 4)).astype(float)
+        index = ([1, 1, 2, 0],
+                 [0, 0, 2, 3])
+        vals = [50, 50, 30, 16]
+
+        _multiarray_tests.test_inplace_increment(a, index, vals)
+        assert_equal(a, [[0.00, 1., 2.0, 19.],
+                         [104., 5., 6.0, 7.0],
+                         [8.00, 9., 40., 11.]])
+
+        b = np.arange(6).astype(float)
+        index = (np.array([1, 2, 0]),)
+        vals = [50, 4, 100.1]
+        _multiarray_tests.test_inplace_increment(b, index, vals)
+        assert_equal(b, [100.1,  51.,   6.,   3.,   4.,   5.])
+
+
+class TestAsCArray:
+    def test_1darray(self):
+        array = np.arange(24, dtype=np.double)
+        from_c = _multiarray_tests.test_as_c_array(array, 3)
+        assert_equal(array[3], from_c)
+
+    def test_2darray(self):
+        array = np.arange(24, dtype=np.double).reshape(3, 8)
+        from_c = _multiarray_tests.test_as_c_array(array, 2, 4)
+        assert_equal(array[2, 4], from_c)
+
+    def test_3darray(self):
+        array = np.arange(24, dtype=np.double).reshape(2, 3, 4)
+        from_c = _multiarray_tests.test_as_c_array(array, 1, 2, 3)
+        assert_equal(array[1, 2, 3], from_c)
+
+
+class TestConversion:
+    def test_array_scalar_relational_operation(self):
+        # All integer
+        for dt1 in np.typecodes['AllInteger']:
+            assert_(1 > np.array(0, dtype=dt1), "type %s failed" % (dt1,))
+            assert_(not 1 < np.array(0, dtype=dt1), "type %s failed" % (dt1,))
+
+            for dt2 in np.typecodes['AllInteger']:
+                assert_(np.array(1, dtype=dt1) > np.array(0, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+                assert_(not np.array(1, dtype=dt1) < np.array(0, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+
+        # Unsigned integers
+        for dt1 in 'BHILQP':
+            assert_(-1 < np.array(1, dtype=dt1), "type %s failed" % (dt1,))
+            assert_(not -1 > np.array(1, dtype=dt1), "type %s failed" % (dt1,))
+            assert_(-1 != np.array(1, dtype=dt1), "type %s failed" % (dt1,))
+
+            # Unsigned vs signed
+            for dt2 in 'bhilqp':
+                assert_(np.array(1, dtype=dt1) > np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+                assert_(not np.array(1, dtype=dt1) < np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+                assert_(np.array(1, dtype=dt1) != np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+
+        # Signed integers and floats
+        for dt1 in 'bhlqp' + np.typecodes['Float']:
+            assert_(1 > np.array(-1, dtype=dt1), "type %s failed" % (dt1,))
+            assert_(not 1 < np.array(-1, dtype=dt1), "type %s failed" % (dt1,))
+            assert_(-1 == np.array(-1, dtype=dt1), "type %s failed" % (dt1,))
+
+            for dt2 in 'bhlqp' + np.typecodes['Float']:
+                assert_(np.array(1, dtype=dt1) > np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+                assert_(not np.array(1, dtype=dt1) < np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+                assert_(np.array(-1, dtype=dt1) == np.array(-1, dtype=dt2),
+                        "type %s and %s failed" % (dt1, dt2))
+
+    def test_to_bool_scalar(self):
+        assert_equal(bool(np.array([False])), False)
+        assert_equal(bool(np.array([True])), True)
+        assert_equal(bool(np.array([[42]])), True)
+        assert_raises(ValueError, bool, np.array([1, 2]))
+
+        class NotConvertible:
+            def __bool__(self):
+                raise NotImplementedError
+
+        assert_raises(NotImplementedError, bool, np.array(NotConvertible()))
+        assert_raises(NotImplementedError, bool, np.array([NotConvertible()]))
+        if IS_PYSTON:
+            pytest.skip("Pyston disables recursion checking")
+
+        self_containing = np.array([None])
+        self_containing[0] = self_containing
+
+        Error = RecursionError
+
+        assert_raises(Error, bool, self_containing)  # previously stack overflow
+        self_containing[0] = None  # resolve circular reference
+
+    def test_to_int_scalar(self):
+        # gh-9972 means that these aren't always the same
+        int_funcs = (int, lambda x: x.__int__())
+        for int_func in int_funcs:
+            assert_equal(int_func(np.array(0)), 0)
+            with assert_warns(DeprecationWarning):
+                assert_equal(int_func(np.array([1])), 1)
+            with assert_warns(DeprecationWarning):
+                assert_equal(int_func(np.array([[42]])), 42)
+            assert_raises(TypeError, int_func, np.array([1, 2]))
+
+            # gh-9972
+            assert_equal(4, int_func(np.array('4')))
+            assert_equal(5, int_func(np.bytes_(b'5')))
+            assert_equal(6, int_func(np.str_('6')))
+
+            # The delegation of int() to __trunc__ was deprecated in
+            # Python 3.11.
+            if sys.version_info < (3, 11):
+                class HasTrunc:
+                    def __trunc__(self):
+                        return 3
+                assert_equal(3, int_func(np.array(HasTrunc())))
+                with assert_warns(DeprecationWarning):
+                    assert_equal(3, int_func(np.array([HasTrunc()])))
+            else:
+                pass
+
+            class NotConvertible:
+                def __int__(self):
+                    raise NotImplementedError
+            assert_raises(NotImplementedError,
+                int_func, np.array(NotConvertible()))
+            with assert_warns(DeprecationWarning):
+                assert_raises(NotImplementedError,
+                    int_func, np.array([NotConvertible()]))
+
+
+class TestWhere:
+    def test_basic(self):
+        dts = [bool, np.int16, np.int32, np.int64, np.double, np.complex128,
+               np.longdouble, np.clongdouble]
+        for dt in dts:
+            c = np.ones(53, dtype=bool)
+            assert_equal(np.where( c, dt(0), dt(1)), dt(0))
+            assert_equal(np.where(~c, dt(0), dt(1)), dt(1))
+            assert_equal(np.where(True, dt(0), dt(1)), dt(0))
+            assert_equal(np.where(False, dt(0), dt(1)), dt(1))
+            d = np.ones_like(c).astype(dt)
+            e = np.zeros_like(d)
+            r = d.astype(dt)
+            c[7] = False
+            r[7] = e[7]
+            assert_equal(np.where(c, e, e), e)
+            assert_equal(np.where(c, d, e), r)
+            assert_equal(np.where(c, d, e[0]), r)
+            assert_equal(np.where(c, d[0], e), r)
+            assert_equal(np.where(c[::2], d[::2], e[::2]), r[::2])
+            assert_equal(np.where(c[1::2], d[1::2], e[1::2]), r[1::2])
+            assert_equal(np.where(c[::3], d[::3], e[::3]), r[::3])
+            assert_equal(np.where(c[1::3], d[1::3], e[1::3]), r[1::3])
+            assert_equal(np.where(c[::-2], d[::-2], e[::-2]), r[::-2])
+            assert_equal(np.where(c[::-3], d[::-3], e[::-3]), r[::-3])
+            assert_equal(np.where(c[1::-3], d[1::-3], e[1::-3]), r[1::-3])
+
+    def test_exotic(self):
+        # object
+        assert_array_equal(np.where(True, None, None), np.array(None))
+        # zero sized
+        m = np.array([], dtype=bool).reshape(0, 3)
+        b = np.array([], dtype=np.float64).reshape(0, 3)
+        assert_array_equal(np.where(m, 0, b), np.array([]).reshape(0, 3))
+
+        # object cast
+        d = np.array([-1.34, -0.16, -0.54, -0.31, -0.08, -0.95, 0.000, 0.313,
+                      0.547, -0.18, 0.876, 0.236, 1.969, 0.310, 0.699, 1.013,
+                      1.267, 0.229, -1.39, 0.487])
+        nan = float('NaN')
+        e = np.array(['5z', '0l', nan, 'Wz', nan, nan, 'Xq', 'cs', nan, nan,
+                     'QN', nan, nan, 'Fd', nan, nan, 'kp', nan, '36', 'i1'],
+                     dtype=object)
+        m = np.array([0, 0, 1, 0, 1, 1, 0, 0, 1, 1,
+                      0, 1, 1, 0, 1, 1, 0, 1, 0, 0], dtype=bool)
+
+        r = e[:]
+        r[np.where(m)] = d[np.where(m)]
+        assert_array_equal(np.where(m, d, e), r)
+
+        r = e[:]
+        r[np.where(~m)] = d[np.where(~m)]
+        assert_array_equal(np.where(m, e, d), r)
+
+        assert_array_equal(np.where(m, e, e), e)
+
+        # minimal dtype result with NaN scalar (e.g required by pandas)
+        d = np.array([1., 2.], dtype=np.float32)
+        e = float('NaN')
+        assert_equal(np.where(True, d, e).dtype, np.float32)
+        e = float('Infinity')
+        assert_equal(np.where(True, d, e).dtype, np.float32)
+        e = float('-Infinity')
+        assert_equal(np.where(True, d, e).dtype, np.float32)
+        # also check upcast
+        e = float(1e150)
+        assert_equal(np.where(True, d, e).dtype, np.float64)
+
+    def test_ndim(self):
+        c = [True, False]
+        a = np.zeros((2, 25))
+        b = np.ones((2, 25))
+        r = np.where(np.array(c)[:,np.newaxis], a, b)
+        assert_array_equal(r[0], a[0])
+        assert_array_equal(r[1], b[0])
+
+        a = a.T
+        b = b.T
+        r = np.where(c, a, b)
+        assert_array_equal(r[:,0], a[:,0])
+        assert_array_equal(r[:,1], b[:,0])
+
+    def test_dtype_mix(self):
+        c = np.array([False, True, False, False, False, False, True, False,
+                     False, False, True, False])
+        a = np.uint32(1)
+        b = np.array([5., 0., 3., 2., -1., -4., 0., -10., 10., 1., 0., 3.],
+                      dtype=np.float64)
+        r = np.array([5., 1., 3., 2., -1., -4., 1., -10., 10., 1., 1., 3.],
+                     dtype=np.float64)
+        assert_equal(np.where(c, a, b), r)
+
+        a = a.astype(np.float32)
+        b = b.astype(np.int64)
+        assert_equal(np.where(c, a, b), r)
+
+        # non bool mask
+        c = c.astype(int)
+        c[c != 0] = 34242324
+        assert_equal(np.where(c, a, b), r)
+        # invert
+        tmpmask = c != 0
+        c[c == 0] = 41247212
+        c[tmpmask] = 0
+        assert_equal(np.where(c, b, a), r)
+
+    def test_foreign(self):
+        c = np.array([False, True, False, False, False, False, True, False,
+                     False, False, True, False])
+        r = np.array([5., 1., 3., 2., -1., -4., 1., -10., 10., 1., 1., 3.],
+                     dtype=np.float64)
+        a = np.ones(1, dtype='>i4')
+        b = np.array([5., 0., 3., 2., -1., -4., 0., -10., 10., 1., 0., 3.],
+                     dtype=np.float64)
+        assert_equal(np.where(c, a, b), r)
+
+        b = b.astype('>f8')
+        assert_equal(np.where(c, a, b), r)
+
+        a = a.astype('<i4')
+        assert_equal(np.where(c, a, b), r)
+
+        c = c.astype('>i4')
+        assert_equal(np.where(c, a, b), r)
+
+    def test_error(self):
+        c = [True, True]
+        a = np.ones((4, 5))
+        b = np.ones((5, 5))
+        assert_raises(ValueError, np.where, c, a, a)
+        assert_raises(ValueError, np.where, c[0], a, b)
+
+    def test_string(self):
+        # gh-4778 check strings are properly filled with nulls
+        a = np.array("abc")
+        b = np.array("x" * 753)
+        assert_equal(np.where(True, a, b), "abc")
+        assert_equal(np.where(False, b, a), "abc")
+
+        # check native datatype sized strings
+        a = np.array("abcd")
+        b = np.array("x" * 8)
+        assert_equal(np.where(True, a, b), "abcd")
+        assert_equal(np.where(False, b, a), "abcd")
+
+    def test_empty_result(self):
+        # pass empty where result through an assignment which reads the data of
+        # empty arrays, error detectable with valgrind, see gh-8922
+        x = np.zeros((1, 1))
+        ibad = np.vstack(np.where(x == 99.))
+        assert_array_equal(ibad,
+                           np.atleast_2d(np.array([[],[]], dtype=np.intp)))
+
+    def test_largedim(self):
+        # invalid read regression gh-9304
+        shape = [10, 2, 3, 4, 5, 6]
+        np.random.seed(2)
+        array = np.random.rand(*shape)
+
+        for i in range(10):
+            benchmark = array.nonzero()
+            result = array.nonzero()
+            assert_array_equal(benchmark, result)
+
+    def test_kwargs(self):
+        a = np.zeros(1)
+        with assert_raises(TypeError):
+            np.where(a, x=a, y=a)
+
+
+if not IS_PYPY:
+    # sys.getsizeof() is not valid on PyPy
+    class TestSizeOf:
+
+        def test_empty_array(self):
+            x = np.array([])
+            assert_(sys.getsizeof(x) > 0)
+
+        def check_array(self, dtype):
+            elem_size = dtype(0).itemsize
+
+            for length in [10, 50, 100, 500]:
+                x = np.arange(length, dtype=dtype)
+                assert_(sys.getsizeof(x) > length * elem_size)
+
+        def test_array_int32(self):
+            self.check_array(np.int32)
+
+        def test_array_int64(self):
+            self.check_array(np.int64)
+
+        def test_array_float32(self):
+            self.check_array(np.float32)
+
+        def test_array_float64(self):
+            self.check_array(np.float64)
+
+        def test_view(self):
+            d = np.ones(100)
+            assert_(sys.getsizeof(d[...]) < sys.getsizeof(d))
+
+        def test_reshape(self):
+            d = np.ones(100)
+            assert_(sys.getsizeof(d) < sys.getsizeof(d.reshape(100, 1, 1).copy()))
+
+        @_no_tracing
+        def test_resize(self):
+            d = np.ones(100)
+            old = sys.getsizeof(d)
+            d.resize(50)
+            assert_(old > sys.getsizeof(d))
+            d.resize(150)
+            assert_(old < sys.getsizeof(d))
+
+        def test_error(self):
+            d = np.ones(100)
+            assert_raises(TypeError, d.__sizeof__, "a")
+
+
+class TestHashing:
+
+    def test_arrays_not_hashable(self):
+        x = np.ones(3)
+        assert_raises(TypeError, hash, x)
+
+    def test_collections_hashable(self):
+        x = np.array([])
+        assert_(not isinstance(x, collections.abc.Hashable))
+
+
+class TestArrayPriority:
+    # This will go away when __array_priority__ is settled, meanwhile
+    # it serves to check unintended changes.
+    op = operator
+    binary_ops = [
+        op.pow, op.add, op.sub, op.mul, op.floordiv, op.truediv, op.mod,
+        op.and_, op.or_, op.xor, op.lshift, op.rshift, op.mod, op.gt,
+        op.ge, op.lt, op.le, op.ne, op.eq
+        ]
+
+    class Foo(np.ndarray):
+        __array_priority__ = 100.
+
+        def __new__(cls, *args, **kwargs):
+            return np.array(*args, **kwargs).view(cls)
+
+    class Bar(np.ndarray):
+        __array_priority__ = 101.
+
+        def __new__(cls, *args, **kwargs):
+            return np.array(*args, **kwargs).view(cls)
+
+    class Other:
+        __array_priority__ = 1000.
+
+        def _all(self, other):
+            return self.__class__()
+
+        __add__ = __radd__ = _all
+        __sub__ = __rsub__ = _all
+        __mul__ = __rmul__ = _all
+        __pow__ = __rpow__ = _all
+        __div__ = __rdiv__ = _all
+        __mod__ = __rmod__ = _all
+        __truediv__ = __rtruediv__ = _all
+        __floordiv__ = __rfloordiv__ = _all
+        __and__ = __rand__ = _all
+        __xor__ = __rxor__ = _all
+        __or__ = __ror__ = _all
+        __lshift__ = __rlshift__ = _all
+        __rshift__ = __rrshift__ = _all
+        __eq__ = _all
+        __ne__ = _all
+        __gt__ = _all
+        __ge__ = _all
+        __lt__ = _all
+        __le__ = _all
+
+    def test_ndarray_subclass(self):
+        a = np.array([1, 2])
+        b = self.Bar([1, 2])
+        for f in self.binary_ops:
+            msg = repr(f)
+            assert_(isinstance(f(a, b), self.Bar), msg)
+            assert_(isinstance(f(b, a), self.Bar), msg)
+
+    def test_ndarray_other(self):
+        a = np.array([1, 2])
+        b = self.Other()
+        for f in self.binary_ops:
+            msg = repr(f)
+            assert_(isinstance(f(a, b), self.Other), msg)
+            assert_(isinstance(f(b, a), self.Other), msg)
+
+    def test_subclass_subclass(self):
+        a = self.Foo([1, 2])
+        b = self.Bar([1, 2])
+        for f in self.binary_ops:
+            msg = repr(f)
+            assert_(isinstance(f(a, b), self.Bar), msg)
+            assert_(isinstance(f(b, a), self.Bar), msg)
+
+    def test_subclass_other(self):
+        a = self.Foo([1, 2])
+        b = self.Other()
+        for f in self.binary_ops:
+            msg = repr(f)
+            assert_(isinstance(f(a, b), self.Other), msg)
+            assert_(isinstance(f(b, a), self.Other), msg)
+
+
+class TestBytestringArrayNonzero:
+
+    def test_empty_bstring_array_is_falsey(self):
+        assert_(not np.array([''], dtype=str))
+
+    def test_whitespace_bstring_array_is_falsey(self):
+        a = np.array(['spam'], dtype=str)
+        a[0] = '  \0\0'
+        assert_(not a)
+
+    def test_all_null_bstring_array_is_falsey(self):
+        a = np.array(['spam'], dtype=str)
+        a[0] = '\0\0\0\0'
+        assert_(not a)
+
+    def test_null_inside_bstring_array_is_truthy(self):
+        a = np.array(['spam'], dtype=str)
+        a[0] = ' \0 \0'
+        assert_(a)
+
+
+class TestUnicodeEncoding:
+    """
+    Tests for encoding related bugs, such as UCS2 vs UCS4, round-tripping
+    issues, etc
+    """
+    def test_round_trip(self):
+        """ Tests that GETITEM, SETITEM, and PyArray_Scalar roundtrip """
+        # gh-15363
+        arr = np.zeros(shape=(), dtype="U1")
+        for i in range(1, sys.maxunicode + 1):
+            expected = chr(i)
+            arr[()] = expected
+            assert arr[()] == expected
+            assert arr.item() == expected
+
+    def test_assign_scalar(self):
+        # gh-3258
+        l = np.array(['aa', 'bb'])
+        l[:] = np.str_('cc')
+        assert_equal(l, ['cc', 'cc'])
+
+    def test_fill_scalar(self):
+        # gh-7227
+        l = np.array(['aa', 'bb'])
+        l.fill(np.str_('cc'))
+        assert_equal(l, ['cc', 'cc'])
+
+
+class TestUnicodeArrayNonzero:
+
+    def test_empty_ustring_array_is_falsey(self):
+        assert_(not np.array([''], dtype=np.str_))
+
+    def test_whitespace_ustring_array_is_falsey(self):
+        a = np.array(['eggs'], dtype=np.str_)
+        a[0] = '  \0\0'
+        assert_(not a)
+
+    def test_all_null_ustring_array_is_falsey(self):
+        a = np.array(['eggs'], dtype=np.str_)
+        a[0] = '\0\0\0\0'
+        assert_(not a)
+
+    def test_null_inside_ustring_array_is_truthy(self):
+        a = np.array(['eggs'], dtype=np.str_)
+        a[0] = ' \0 \0'
+        assert_(a)
+
+
+class TestFormat:
+
+    def test_0d(self):
+        a = np.array(np.pi)
+        assert_equal('{:0.3g}'.format(a), '3.14')
+        assert_equal('{:0.3g}'.format(a[()]), '3.14')
+
+    def test_1d_no_format(self):
+        a = np.array([np.pi])
+        assert_equal('{}'.format(a), str(a))
+
+    def test_1d_format(self):
+        # until gh-5543, ensure that the behaviour matches what it used to be
+        a = np.array([np.pi])
+        assert_raises(TypeError, '{:30}'.format, a)
+
+from numpy.testing import IS_PYPY
+
+class TestCTypes:
+
+    def test_ctypes_is_available(self):
+        test_arr = np.array([[1, 2, 3], [4, 5, 6]])
+
+        assert_equal(ctypes, test_arr.ctypes._ctypes)
+        assert_equal(tuple(test_arr.ctypes.shape), (2, 3))
+
+    def test_ctypes_is_not_available(self):
+        from numpy.core import _internal
+        _internal.ctypes = None
+        try:
+            test_arr = np.array([[1, 2, 3], [4, 5, 6]])
+
+            assert_(isinstance(test_arr.ctypes._ctypes,
+                               _internal._missing_ctypes))
+            assert_equal(tuple(test_arr.ctypes.shape), (2, 3))
+        finally:
+            _internal.ctypes = ctypes
+
+    def _make_readonly(x):
+        x.flags.writeable = False
+        return x
+
+    @pytest.mark.parametrize('arr', [
+        np.array([1, 2, 3]),
+        np.array([['one', 'two'], ['three', 'four']]),
+        np.array((1, 2), dtype='i4,i4'),
+        np.zeros((2,), dtype=
+            np.dtype(dict(
+                formats=['<i4', '<i4'],
+                names=['a', 'b'],
+                offsets=[0, 2],
+                itemsize=6
+            ))
+        ),
+        np.array([None], dtype=object),
+        np.array([]),
+        np.empty((0, 0)),
+        _make_readonly(np.array([1, 2, 3])),
+    ], ids=[
+        '1d',
+        '2d',
+        'structured',
+        'overlapping',
+        'object',
+        'empty',
+        'empty-2d',
+        'readonly'
+    ])
+    def test_ctypes_data_as_holds_reference(self, arr):
+        # gh-9647
+        # create a copy to ensure that pytest does not mess with the refcounts
+        arr = arr.copy()
+
+        arr_ref = weakref.ref(arr)
+
+        ctypes_ptr = arr.ctypes.data_as(ctypes.c_void_p)
+
+        # `ctypes_ptr` should hold onto `arr`
+        del arr
+        break_cycles()
+        assert_(arr_ref() is not None, "ctypes pointer did not hold onto a reference")
+
+        # but when the `ctypes_ptr` object dies, so should `arr`
+        del ctypes_ptr
+        if IS_PYPY:
+            # Pypy does not recycle arr objects immediately. Trigger gc to
+            # release arr. Cpython uses refcounts. An explicit call to gc
+            # should not be needed here.
+            break_cycles()
+        assert_(arr_ref() is None, "unknowable whether ctypes pointer holds a reference")
+
+    def test_ctypes_as_parameter_holds_reference(self):
+        arr = np.array([None]).copy()
+
+        arr_ref = weakref.ref(arr)
+
+        ctypes_ptr = arr.ctypes._as_parameter_
+
+        # `ctypes_ptr` should hold onto `arr`
+        del arr
+        break_cycles()
+        assert_(arr_ref() is not None, "ctypes pointer did not hold onto a reference")
+
+        # but when the `ctypes_ptr` object dies, so should `arr`
+        del ctypes_ptr
+        if IS_PYPY:
+            break_cycles()
+        assert_(arr_ref() is None, "unknowable whether ctypes pointer holds a reference")
+
+
+class TestWritebackIfCopy:
+    # all these tests use the WRITEBACKIFCOPY mechanism
+    def test_argmax_with_out(self):
+        mat = np.eye(5)
+        out = np.empty(5, dtype='i2')
+        res = np.argmax(mat, 0, out=out)
+        assert_equal(res, range(5))
+
+    def test_argmin_with_out(self):
+        mat = -np.eye(5)
+        out = np.empty(5, dtype='i2')
+        res = np.argmin(mat, 0, out=out)
+        assert_equal(res, range(5))
+
+    def test_insert_noncontiguous(self):
+        a = np.arange(6).reshape(2,3).T # force non-c-contiguous
+        # uses arr_insert
+        np.place(a, a>2, [44, 55])
+        assert_equal(a, np.array([[0, 44], [1, 55], [2, 44]]))
+        # hit one of the failing paths
+        assert_raises(ValueError, np.place, a, a>20, [])
+
+    def test_put_noncontiguous(self):
+        a = np.arange(6).reshape(2,3).T # force non-c-contiguous
+        np.put(a, [0, 2], [44, 55])
+        assert_equal(a, np.array([[44, 3], [55, 4], [2, 5]]))
+
+    def test_putmask_noncontiguous(self):
+        a = np.arange(6).reshape(2,3).T # force non-c-contiguous
+        # uses arr_putmask
+        np.putmask(a, a>2, a**2)
+        assert_equal(a, np.array([[0, 9], [1, 16], [2, 25]]))
+
+    def test_take_mode_raise(self):
+        a = np.arange(6, dtype='int')
+        out = np.empty(2, dtype='int')
+        np.take(a, [0, 2], out=out, mode='raise')
+        assert_equal(out, np.array([0, 2]))
+
+    def test_choose_mod_raise(self):
+        a = np.array([[1, 0, 1], [0, 1, 0], [1, 0, 1]])
+        out = np.empty((3,3), dtype='int')
+        choices = [-10, 10]
+        np.choose(a, choices, out=out, mode='raise')
+        assert_equal(out, np.array([[ 10, -10,  10],
+                                    [-10,  10, -10],
+                                    [ 10, -10,  10]]))
+
+    def test_flatiter__array__(self):
+        a = np.arange(9).reshape(3,3)
+        b = a.T.flat
+        c = b.__array__()
+        # triggers the WRITEBACKIFCOPY resolution, assuming refcount semantics
+        del c
+
+    def test_dot_out(self):
+        # if HAVE_CBLAS, will use WRITEBACKIFCOPY
+        a = np.arange(9, dtype=float).reshape(3,3)
+        b = np.dot(a, a, out=a)
+        assert_equal(b, np.array([[15, 18, 21], [42, 54, 66], [69, 90, 111]]))
+
+    def test_view_assign(self):
+        from numpy.core._multiarray_tests import npy_create_writebackifcopy, npy_resolve
+
+        arr = np.arange(9).reshape(3, 3).T
+        arr_wb = npy_create_writebackifcopy(arr)
+        assert_(arr_wb.flags.writebackifcopy)
+        assert_(arr_wb.base is arr)
+        arr_wb[...] = -100
+        npy_resolve(arr_wb)
+        # arr changes after resolve, even though we assigned to arr_wb
+        assert_equal(arr, -100)
+        # after resolve, the two arrays no longer reference each other
+        assert_(arr_wb.ctypes.data != 0)
+        assert_equal(arr_wb.base, None)
+        # assigning to arr_wb does not get transferred to arr
+        arr_wb[...] = 100
+        assert_equal(arr, -100)
+
+    @pytest.mark.leaks_references(
+            reason="increments self in dealloc; ignore since deprecated path.")
+    def test_dealloc_warning(self):
+        with suppress_warnings() as sup:
+            sup.record(RuntimeWarning)
+            arr = np.arange(9).reshape(3, 3)
+            v = arr.T
+            _multiarray_tests.npy_abuse_writebackifcopy(v)
+            assert len(sup.log) == 1
+
+    def test_view_discard_refcount(self):
+        from numpy.core._multiarray_tests import npy_create_writebackifcopy, npy_discard
+
+        arr = np.arange(9).reshape(3, 3).T
+        orig = arr.copy()
+        if HAS_REFCOUNT:
+            arr_cnt = sys.getrefcount(arr)
+        arr_wb = npy_create_writebackifcopy(arr)
+        assert_(arr_wb.flags.writebackifcopy)
+        assert_(arr_wb.base is arr)
+        arr_wb[...] = -100
+        npy_discard(arr_wb)
+        # arr remains unchanged after discard
+        assert_equal(arr, orig)
+        # after discard, the two arrays no longer reference each other
+        assert_(arr_wb.ctypes.data != 0)
+        assert_equal(arr_wb.base, None)
+        if HAS_REFCOUNT:
+            assert_equal(arr_cnt, sys.getrefcount(arr))
+        # assigning to arr_wb does not get transferred to arr
+        arr_wb[...] = 100
+        assert_equal(arr, orig)
+
+
+class TestArange:
+    def test_infinite(self):
+        assert_raises_regex(
+            ValueError, "size exceeded",
+            np.arange, 0, np.inf
+        )
+
+    def test_nan_step(self):
+        assert_raises_regex(
+            ValueError, "cannot compute length",
+            np.arange, 0, 1, np.nan
+        )
+
+    def test_zero_step(self):
+        assert_raises(ZeroDivisionError, np.arange, 0, 10, 0)
+        assert_raises(ZeroDivisionError, np.arange, 0.0, 10.0, 0.0)
+
+        # empty range
+        assert_raises(ZeroDivisionError, np.arange, 0, 0, 0)
+        assert_raises(ZeroDivisionError, np.arange, 0.0, 0.0, 0.0)
+
+    def test_require_range(self):
+        assert_raises(TypeError, np.arange)
+        assert_raises(TypeError, np.arange, step=3)
+        assert_raises(TypeError, np.arange, dtype='int64')
+        assert_raises(TypeError, np.arange, start=4)
+
+    def test_start_stop_kwarg(self):
+        keyword_stop = np.arange(stop=3)
+        keyword_zerotostop = np.arange(start=0, stop=3)
+        keyword_start_stop = np.arange(start=3, stop=9)
+
+        assert len(keyword_stop) == 3
+        assert len(keyword_zerotostop) == 3
+        assert len(keyword_start_stop) == 6
+        assert_array_equal(keyword_stop, keyword_zerotostop)
+
+    def test_arange_booleans(self):
+        # Arange makes some sense for booleans and works up to length 2.
+        # But it is weird since `arange(2, 4, dtype=bool)` works.
+        # Arguably, much or all of this could be deprecated/removed.
+        res = np.arange(False, dtype=bool)
+        assert_array_equal(res, np.array([], dtype="bool"))
+
+        res = np.arange(True, dtype="bool")
+        assert_array_equal(res, [False])
+
+        res = np.arange(2, dtype="bool")
+        assert_array_equal(res, [False, True])
+
+        # This case is especially weird, but drops out without special case:
+        res = np.arange(6, 8, dtype="bool")
+        assert_array_equal(res, [True, True])
+
+        with pytest.raises(TypeError):
+            np.arange(3, dtype="bool")
+
+    @pytest.mark.parametrize("dtype", ["S3", "U", "5i"])
+    def test_rejects_bad_dtypes(self, dtype):
+        dtype = np.dtype(dtype)
+        DType_name = re.escape(str(type(dtype)))
+        with pytest.raises(TypeError,
+                match=rf"arange\(\) not supported for inputs .* {DType_name}"):
+            np.arange(2, dtype=dtype)
+
+    def test_rejects_strings(self):
+        # Explicitly test error for strings which may call "b" - "a":
+        DType_name = re.escape(str(type(np.array("a").dtype)))
+        with pytest.raises(TypeError,
+                match=rf"arange\(\) not supported for inputs .* {DType_name}"):
+            np.arange("a", "b")
+
+    def test_byteswapped(self):
+        res_be = np.arange(1, 1000, dtype=">i4")
+        res_le = np.arange(1, 1000, dtype="<i4")
+        assert res_be.dtype == ">i4"
+        assert res_le.dtype == "<i4"
+        assert_array_equal(res_le, res_be)
+
+    @pytest.mark.parametrize("which", [0, 1, 2])
+    def test_error_paths_and_promotion(self, which):
+        args = [0, 1, 2]  # start, stop, and step
+        args[which] = np.float64(2.)  # should ensure float64 output
+
+        assert np.arange(*args).dtype == np.float64
+
+        # Cover stranger error path, test only to achieve code coverage!
+        args[which] = [None, []]
+        with pytest.raises(ValueError):
+            # Fails discovering start dtype
+            np.arange(*args)
+
+
+class TestArrayFinalize:
+    """ Tests __array_finalize__ """
+
+    def test_receives_base(self):
+        # gh-11237
+        class SavesBase(np.ndarray):
+            def __array_finalize__(self, obj):
+                self.saved_base = self.base
+
+        a = np.array(1).view(SavesBase)
+        assert_(a.saved_base is a.base)
+
+    def test_bad_finalize1(self):
+        class BadAttributeArray(np.ndarray):
+            @property
+            def __array_finalize__(self):
+                raise RuntimeError("boohoo!")
+
+        with pytest.raises(TypeError, match="not callable"):
+            np.arange(10).view(BadAttributeArray)
+
+    def test_bad_finalize2(self):
+        class BadAttributeArray(np.ndarray):
+            def __array_finalize__(self):
+                raise RuntimeError("boohoo!")
+
+        with pytest.raises(TypeError, match="takes 1 positional"):
+            np.arange(10).view(BadAttributeArray)
+
+    def test_bad_finalize3(self):
+        class BadAttributeArray(np.ndarray):
+            def __array_finalize__(self, obj):
+                raise RuntimeError("boohoo!")
+
+        with pytest.raises(RuntimeError, match="boohoo!"):
+            np.arange(10).view(BadAttributeArray)
+
+    def test_lifetime_on_error(self):
+        # gh-11237
+        class RaisesInFinalize(np.ndarray):
+            def __array_finalize__(self, obj):
+                # crash, but keep this object alive
+                raise Exception(self)
+
+        # a plain object can't be weakref'd
+        class Dummy: pass
+
+        # get a weak reference to an object within an array
+        obj_arr = np.array(Dummy())
+        obj_ref = weakref.ref(obj_arr[()])
+
+        # get an array that crashed in __array_finalize__
+        with assert_raises(Exception) as e:
+            obj_arr.view(RaisesInFinalize)
+
+        obj_subarray = e.exception.args[0]
+        del e
+        assert_(isinstance(obj_subarray, RaisesInFinalize))
+
+        # reference should still be held by obj_arr
+        break_cycles()
+        assert_(obj_ref() is not None, "object should not already be dead")
+
+        del obj_arr
+        break_cycles()
+        assert_(obj_ref() is not None, "obj_arr should not hold the last reference")
+
+        del obj_subarray
+        break_cycles()
+        assert_(obj_ref() is None, "no references should remain")
+
+    def test_can_use_super(self):
+        class SuperFinalize(np.ndarray):
+            def __array_finalize__(self, obj):
+                self.saved_result = super().__array_finalize__(obj)
+
+        a = np.array(1).view(SuperFinalize)
+        assert_(a.saved_result is None)
+
+
+def test_orderconverter_with_nonASCII_unicode_ordering():
+    # gh-7475
+    a = np.arange(5)
+    assert_raises(ValueError, a.flatten, order='\xe2')
+
+
+def test_equal_override():
+    # gh-9153: ndarray.__eq__ uses special logic for structured arrays, which
+    # did not respect overrides with __array_priority__ or __array_ufunc__.
+    # The PR fixed this for __array_priority__ and __array_ufunc__ = None.
+    class MyAlwaysEqual:
+        def __eq__(self, other):
+            return "eq"
+
+        def __ne__(self, other):
+            return "ne"
+
+    class MyAlwaysEqualOld(MyAlwaysEqual):
+        __array_priority__ = 10000
+
+    class MyAlwaysEqualNew(MyAlwaysEqual):
+        __array_ufunc__ = None
+
+    array = np.array([(0, 1), (2, 3)], dtype='i4,i4')
+    for my_always_equal_cls in MyAlwaysEqualOld, MyAlwaysEqualNew:
+        my_always_equal = my_always_equal_cls()
+        assert_equal(my_always_equal == array, 'eq')
+        assert_equal(array == my_always_equal, 'eq')
+        assert_equal(my_always_equal != array, 'ne')
+        assert_equal(array != my_always_equal, 'ne')
+
+
+@pytest.mark.parametrize("op", [operator.eq, operator.ne])
+@pytest.mark.parametrize(["dt1", "dt2"], [
+        ([("f", "i")], [("f", "i")]),  # structured comparison (successful)
+        ("M8", "d"),  # impossible comparison: result is all True or False
+        ("d", "d"),  # valid comparison
+        ])
+def test_equal_subclass_no_override(op, dt1, dt2):
+    # Test how the three different possible code-paths deal with subclasses
+
+    class MyArr(np.ndarray):
+        called_wrap = 0
+
+        def __array_wrap__(self, new):
+            type(self).called_wrap += 1
+            return super().__array_wrap__(new)
+
+    numpy_arr = np.zeros(5, dtype=dt1)
+    my_arr = np.zeros(5, dtype=dt2).view(MyArr)
+
+    assert type(op(numpy_arr, my_arr)) is MyArr
+    assert type(op(my_arr, numpy_arr)) is MyArr
+    # We expect 2 calls (more if there were more fields):
+    assert MyArr.called_wrap == 2
+
+
+@pytest.mark.parametrize(["dt1", "dt2"], [
+        ("M8[ns]", "d"),
+        ("M8[s]", "l"),
+        ("m8[ns]", "d"),
+        # Missing: ("m8[ns]", "l") as timedelta currently promotes ints
+        ("M8[s]", "m8[s]"),
+        ("S5", "U5"),
+        # Structured/void dtypes have explicit paths not tested here.
+])
+def test_no_loop_gives_all_true_or_false(dt1, dt2):
+    # Make sure they broadcast to test result shape, use random values, since
+    # the actual value should be ignored
+    arr1 = np.random.randint(5, size=100).astype(dt1)
+    arr2 = np.random.randint(5, size=99)[:, np.newaxis].astype(dt2)
+
+    res = arr1 == arr2
+    assert res.shape == (99, 100)
+    assert res.dtype == bool
+    assert not res.any()
+
+    res = arr1 != arr2
+    assert res.shape == (99, 100)
+    assert res.dtype == bool
+    assert res.all()
+
+    # incompatible shapes raise though
+    arr2 = np.random.randint(5, size=99).astype(dt2)
+    with pytest.raises(ValueError):
+        arr1 == arr2
+
+    with pytest.raises(ValueError):
+        arr1 != arr2
+
+    # Basic test with another operation:
+    with pytest.raises(np.core._exceptions._UFuncNoLoopError):
+        arr1 > arr2
+
+
+@pytest.mark.parametrize("op", [
+        operator.eq, operator.ne, operator.le, operator.lt, operator.ge,
+        operator.gt])
+def test_comparisons_forwards_error(op):
+    class NotArray:
+        def __array__(self):
+            raise TypeError("run you fools")
+
+    with pytest.raises(TypeError, match="run you fools"):
+        op(np.arange(2), NotArray())
+
+    with pytest.raises(TypeError, match="run you fools"):
+        op(NotArray(), np.arange(2))
+
+
+def test_richcompare_scalar_boolean_singleton_return():
+    # These are currently guaranteed to be the boolean singletons, but maybe
+    # returning NumPy booleans would also be OK:
+    assert (np.array(0) == "a") is False
+    assert (np.array(0) != "a") is True
+    assert (np.int16(0) == "a") is False
+    assert (np.int16(0) != "a") is True
+
+
+@pytest.mark.parametrize("op", [
+        operator.eq, operator.ne, operator.le, operator.lt, operator.ge,
+        operator.gt])
+def test_ragged_comparison_fails(op):
+    # This needs to convert the internal array to True/False, which fails:
+    a = np.array([1, np.array([1, 2, 3])], dtype=object)
+    b = np.array([1, np.array([1, 2, 3])], dtype=object)
+
+    with pytest.raises(ValueError, match="The truth value.*ambiguous"):
+        op(a, b)
+
+
+@pytest.mark.parametrize(
+    ["fun", "npfun"],
+    [
+        (_multiarray_tests.npy_cabs, np.absolute),
+        (_multiarray_tests.npy_carg, np.angle)
+    ]
+)
+@pytest.mark.parametrize("x", [1, np.inf, -np.inf, np.nan])
+@pytest.mark.parametrize("y", [1, np.inf, -np.inf, np.nan])
+@pytest.mark.parametrize("test_dtype", np.complexfloating.__subclasses__())
+def test_npymath_complex(fun, npfun, x, y, test_dtype):
+    # Smoketest npymath functions
+    z = test_dtype(complex(x, y))
+    with np.errstate(invalid='ignore'):
+        # Fallback implementations may emit a warning for +-inf (see gh-24876):
+        #     RuntimeWarning: invalid value encountered in absolute
+        got = fun(z)
+        expected = npfun(z)
+        assert_allclose(got, expected)
+
+
+def test_npymath_real():
+    # Smoketest npymath functions
+    from numpy.core._multiarray_tests import (
+        npy_log10, npy_cosh, npy_sinh, npy_tan, npy_tanh)
+
+    funcs = {npy_log10: np.log10,
+             npy_cosh: np.cosh,
+             npy_sinh: np.sinh,
+             npy_tan: np.tan,
+             npy_tanh: np.tanh}
+    vals = (1, np.inf, -np.inf, np.nan)
+    types = (np.float32, np.float64, np.longdouble)
+
+    with np.errstate(all='ignore'):
+        for fun, npfun in funcs.items():
+            for x, t in itertools.product(vals, types):
+                z = t(x)
+                got = fun(z)
+                expected = npfun(z)
+                assert_allclose(got, expected)
+
+def test_uintalignment_and_alignment():
+    # alignment code needs to satisfy these requirements:
+    #  1. numpy structs match C struct layout
+    #  2. ufuncs/casting is safe wrt to aligned access
+    #  3. copy code is safe wrt to "uint alidned" access
+    #
+    # Complex types are the main problem, whose alignment may not be the same
+    # as their "uint alignment".
+    #
+    # This test might only fail on certain platforms, where uint64 alignment is
+    # not equal to complex64 alignment. The second 2 tests will only fail
+    # for DEBUG=1.
+
+    d1 = np.dtype('u1,c8', align=True)
+    d2 = np.dtype('u4,c8', align=True)
+    d3 = np.dtype({'names': ['a', 'b'], 'formats': ['u1', d1]}, align=True)
+
+    assert_equal(np.zeros(1, dtype=d1)['f1'].flags['ALIGNED'], True)
+    assert_equal(np.zeros(1, dtype=d2)['f1'].flags['ALIGNED'], True)
+    assert_equal(np.zeros(1, dtype='u1,c8')['f1'].flags['ALIGNED'], False)
+
+    # check that C struct matches numpy struct size
+    s = _multiarray_tests.get_struct_alignments()
+    for d, (alignment, size) in zip([d1,d2,d3], s):
+        assert_equal(d.alignment, alignment)
+        assert_equal(d.itemsize, size)
+
+    # check that ufuncs don't complain in debug mode
+    # (this is probably OK if the aligned flag is true above)
+    src = np.zeros((2,2), dtype=d1)['f1']  # 4-byte aligned, often
+    np.exp(src)  # assert fails?
+
+    # check that copy code doesn't complain in debug mode
+    dst = np.zeros((2,2), dtype='c8')
+    dst[:,1] = src[:,1]  # assert in lowlevel_strided_loops fails?
+
+class TestAlignment:
+    # adapted from scipy._lib.tests.test__util.test__aligned_zeros
+    # Checks that unusual memory alignments don't trip up numpy.
+    # In particular, check RELAXED_STRIDES don't trip alignment assertions in
+    # NDEBUG mode for size-0 arrays (gh-12503)
+
+    def check(self, shape, dtype, order, align):
+        err_msg = repr((shape, dtype, order, align))
+        x = _aligned_zeros(shape, dtype, order, align=align)
+        if align is None:
+            align = np.dtype(dtype).alignment
+        assert_equal(x.__array_interface__['data'][0] % align, 0)
+        if hasattr(shape, '__len__'):
+            assert_equal(x.shape, shape, err_msg)
+        else:
+            assert_equal(x.shape, (shape,), err_msg)
+        assert_equal(x.dtype, dtype)
+        if order == "C":
+            assert_(x.flags.c_contiguous, err_msg)
+        elif order == "F":
+            if x.size > 0:
+                assert_(x.flags.f_contiguous, err_msg)
+        elif order is None:
+            assert_(x.flags.c_contiguous, err_msg)
+        else:
+            raise ValueError()
+
+    def test_various_alignments(self):
+        for align in [1, 2, 3, 4, 8, 12, 16, 32, 64, None]:
+            for n in [0, 1, 3, 11]:
+                for order in ["C", "F", None]:
+                    for dtype in list(np.typecodes["All"]) + ['i4,i4,i4']:
+                        if dtype == 'O':
+                            # object dtype can't be misaligned
+                            continue
+                        for shape in [n, (1, 2, 3, n)]:
+                            self.check(shape, np.dtype(dtype), order, align)
+
+    def test_strided_loop_alignments(self):
+        # particularly test that complex64 and float128 use right alignment
+        # code-paths, since these are particularly problematic. It is useful to
+        # turn on USE_DEBUG for this test, so lowlevel-loop asserts are run.
+        for align in [1, 2, 4, 8, 12, 16, None]:
+            xf64 = _aligned_zeros(3, np.float64)
+
+            xc64 = _aligned_zeros(3, np.complex64, align=align)
+            xf128 = _aligned_zeros(3, np.longdouble, align=align)
+
+            # test casting, both to and from misaligned
+            with suppress_warnings() as sup:
+                sup.filter(np.ComplexWarning, "Casting complex values")
+                xc64.astype('f8')
+            xf64.astype(np.complex64)
+            test = xc64 + xf64
+
+            xf128.astype('f8')
+            xf64.astype(np.longdouble)
+            test = xf128 + xf64
+
+            test = xf128 + xc64
+
+            # test copy, both to and from misaligned
+            # contig copy
+            xf64[:] = xf64.copy()
+            xc64[:] = xc64.copy()
+            xf128[:] = xf128.copy()
+            # strided copy
+            xf64[::2] = xf64[::2].copy()
+            xc64[::2] = xc64[::2].copy()
+            xf128[::2] = xf128[::2].copy()
+
+def test_getfield():
+    a = np.arange(32, dtype='uint16')
+    if sys.byteorder == 'little':
+        i = 0
+        j = 1
+    else:
+        i = 1
+        j = 0
+    b = a.getfield('int8', i)
+    assert_equal(b, a)
+    b = a.getfield('int8', j)
+    assert_equal(b, 0)
+    pytest.raises(ValueError, a.getfield, 'uint8', -1)
+    pytest.raises(ValueError, a.getfield, 'uint8', 16)
+    pytest.raises(ValueError, a.getfield, 'uint64', 0)
+
+
+class TestViewDtype:
+    """
+    Verify that making a view of a non-contiguous array works as expected.
+    """
+    def test_smaller_dtype_multiple(self):
+        # x is non-contiguous
+        x = np.arange(10, dtype='<i4')[::2]
+        with pytest.raises(ValueError,
+                           match='the last axis must be contiguous'):
+            x.view('<i2')
+        expected = [[0, 0], [2, 0], [4, 0], [6, 0], [8, 0]]
+        assert_array_equal(x[:, np.newaxis].view('<i2'), expected)
+
+    def test_smaller_dtype_not_multiple(self):
+        # x is non-contiguous
+        x = np.arange(5, dtype='<i4')[::2]
+
+        with pytest.raises(ValueError,
+                           match='the last axis must be contiguous'):
+            x.view('S3')
+        with pytest.raises(ValueError,
+                           match='When changing to a smaller dtype'):
+            x[:, np.newaxis].view('S3')
+
+        # Make sure the problem is because of the dtype size
+        expected = [[b''], [b'\x02'], [b'\x04']]
+        assert_array_equal(x[:, np.newaxis].view('S4'), expected)
+
+    def test_larger_dtype_multiple(self):
+        # x is non-contiguous in the first dimension, contiguous in the last
+        x = np.arange(20, dtype='<i2').reshape(10, 2)[::2, :]
+        expected = np.array([[65536], [327684], [589832],
+                             [851980], [1114128]], dtype='<i4')
+        assert_array_equal(x.view('<i4'), expected)
+
+    def test_larger_dtype_not_multiple(self):
+        # x is non-contiguous in the first dimension, contiguous in the last
+        x = np.arange(20, dtype='<i2').reshape(10, 2)[::2, :]
+        with pytest.raises(ValueError,
+                           match='When changing to a larger dtype'):
+            x.view('S3')
+        # Make sure the problem is because of the dtype size
+        expected = [[b'\x00\x00\x01'], [b'\x04\x00\x05'], [b'\x08\x00\t'],
+                    [b'\x0c\x00\r'], [b'\x10\x00\x11']]
+        assert_array_equal(x.view('S4'), expected)
+
+    def test_f_contiguous(self):
+        # x is F-contiguous
+        x = np.arange(4 * 3, dtype='<i4').reshape(4, 3).T
+        with pytest.raises(ValueError,
+                           match='the last axis must be contiguous'):
+            x.view('<i2')
+
+    def test_non_c_contiguous(self):
+        # x is contiguous in axis=-1, but not C-contiguous in other axes
+        x = np.arange(2 * 3 * 4, dtype='i1').\
+                    reshape(2, 3, 4).transpose(1, 0, 2)
+        expected = [[[256, 770], [3340, 3854]],
+                    [[1284, 1798], [4368, 4882]],
+                    [[2312, 2826], [5396, 5910]]]
+        assert_array_equal(x.view('<i2'), expected)
+
+
+@pytest.mark.xfail(_SUPPORTS_SVE, reason="gh-22982")
+# Test various array sizes that hit different code paths in quicksort-avx512
+@pytest.mark.parametrize("N", np.arange(1, 512))
+@pytest.mark.parametrize("dtype", ['e', 'f', 'd'])
+def test_sort_float(N, dtype):
+    # Regular data with nan sprinkled
+    np.random.seed(42)
+    arr = -0.5 + np.random.sample(N).astype(dtype)
+    arr[np.random.choice(arr.shape[0], 3)] = np.nan
+    assert_equal(np.sort(arr, kind='quick'), np.sort(arr, kind='heap'))
+
+    # (2) with +INF
+    infarr = np.inf*np.ones(N, dtype=dtype)
+    infarr[np.random.choice(infarr.shape[0], 5)] = -1.0
+    assert_equal(np.sort(infarr, kind='quick'), np.sort(infarr, kind='heap'))
+
+    # (3) with -INF
+    neginfarr = -np.inf*np.ones(N, dtype=dtype)
+    neginfarr[np.random.choice(neginfarr.shape[0], 5)] = 1.0
+    assert_equal(np.sort(neginfarr, kind='quick'),
+                 np.sort(neginfarr, kind='heap'))
+
+    # (4) with +/-INF
+    infarr = np.inf*np.ones(N, dtype=dtype)
+    infarr[np.random.choice(infarr.shape[0], (int)(N/2))] = -np.inf
+    assert_equal(np.sort(infarr, kind='quick'), np.sort(infarr, kind='heap'))
+
+def test_sort_float16():
+    arr = np.arange(65536, dtype=np.int16)
+    temp = np.frombuffer(arr.tobytes(), dtype=np.float16)
+    data = np.copy(temp)
+    np.random.shuffle(data)
+    data_backup = data
+    assert_equal(np.sort(data, kind='quick'),
+            np.sort(data_backup, kind='heap'))
+
+
+@pytest.mark.parametrize("N", np.arange(1, 512))
+@pytest.mark.parametrize("dtype", ['h', 'H', 'i', 'I', 'l', 'L'])
+def test_sort_int(N, dtype):
+    # Random data with MAX and MIN sprinkled
+    minv = np.iinfo(dtype).min
+    maxv = np.iinfo(dtype).max
+    arr = np.random.randint(low=minv, high=maxv-1, size=N, dtype=dtype)
+    arr[np.random.choice(arr.shape[0], 10)] = minv
+    arr[np.random.choice(arr.shape[0], 10)] = maxv
+    assert_equal(np.sort(arr, kind='quick'), np.sort(arr, kind='heap'))
+
+
+def test_sort_uint():
+    # Random data with NPY_MAX_UINT32 sprinkled
+    rng = np.random.default_rng(42)
+    N = 2047
+    maxv = np.iinfo(np.uint32).max
+    arr = rng.integers(low=0, high=maxv, size=N).astype('uint32')
+    arr[np.random.choice(arr.shape[0], 10)] = maxv
+    assert_equal(np.sort(arr, kind='quick'), np.sort(arr, kind='heap'))
+
+def test_private_get_ndarray_c_version():
+    assert isinstance(_get_ndarray_c_version(), int)
+
+
+@pytest.mark.parametrize("N", np.arange(1, 512))
+@pytest.mark.parametrize("dtype", [np.float32, np.float64])
+def test_argsort_float(N, dtype):
+    rnd = np.random.RandomState(116112)
+    # (1) Regular data with a few nan: doesn't use vectorized sort
+    arr = -0.5 + rnd.random(N).astype(dtype)
+    arr[rnd.choice(arr.shape[0], 3)] = np.nan
+    assert_arg_sorted(arr, np.argsort(arr, kind='quick'))
+
+    # (2) Random data with inf at the end of array
+    # See: https://github.com/intel/x86-simd-sort/pull/39
+    arr = -0.5 + rnd.rand(N).astype(dtype)
+    arr[N-1] = np.inf
+    assert_arg_sorted(arr, np.argsort(arr, kind='quick'))
+
+
+@pytest.mark.parametrize("N", np.arange(2, 512))
+@pytest.mark.parametrize("dtype", [np.int32, np.uint32, np.int64, np.uint64])
+def test_argsort_int(N, dtype):
+    rnd = np.random.RandomState(1100710816)
+    # (1) random data with min and max values
+    minv = np.iinfo(dtype).min
+    maxv = np.iinfo(dtype).max
+    arr = rnd.randint(low=minv, high=maxv, size=N, dtype=dtype)
+    i, j = rnd.choice(N, 2, replace=False)
+    arr[i] = minv
+    arr[j] = maxv
+    assert_arg_sorted(arr, np.argsort(arr, kind='quick'))
+
+    # (2) random data with max value at the end of array
+    # See: https://github.com/intel/x86-simd-sort/pull/39
+    arr = rnd.randint(low=minv, high=maxv, size=N, dtype=dtype)
+    arr[N-1] = maxv
+    assert_arg_sorted(arr, np.argsort(arr, kind='quick'))
+
+
+@pytest.mark.skipif(not HAS_REFCOUNT, reason="Python lacks refcounts")
+def test_gh_22683():
+    b = 777.68760986
+    a = np.array([b] * 10000, dtype=object)
+    refc_start = sys.getrefcount(b)
+    np.choose(np.zeros(10000, dtype=int), [a], out=a)
+    np.choose(np.zeros(10000, dtype=int), [a], out=a)
+    refc_end = sys.getrefcount(b)
+    assert refc_end - refc_start < 10
+
+
+def test_gh_24459():
+    a = np.zeros((50, 3), dtype=np.float64)
+    with pytest.raises(TypeError):
+        np.choose(a, [3, -1])