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+#!/usr/bin/env python3
+
+# Copyright (c) 2009, Giampaolo Rodola'. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Linux specific tests."""
+
+from __future__ import division
+
+import collections
+import contextlib
+import errno
+import io
+import os
+import re
+import shutil
+import socket
+import struct
+import textwrap
+import time
+import warnings
+
+import psutil
+from psutil import LINUX
+from psutil._compat import PY3
+from psutil._compat import FileNotFoundError
+from psutil._compat import basestring
+from psutil.tests import AARCH64
+from psutil.tests import GITHUB_ACTIONS
+from psutil.tests import GLOBAL_TIMEOUT
+from psutil.tests import HAS_BATTERY
+from psutil.tests import HAS_CPU_FREQ
+from psutil.tests import HAS_GETLOADAVG
+from psutil.tests import HAS_RLIMIT
+from psutil.tests import PYPY
+from psutil.tests import PYTEST_PARALLEL
+from psutil.tests import QEMU_USER
+from psutil.tests import TOLERANCE_DISK_USAGE
+from psutil.tests import TOLERANCE_SYS_MEM
+from psutil.tests import PsutilTestCase
+from psutil.tests import ThreadTask
+from psutil.tests import call_until
+from psutil.tests import mock
+from psutil.tests import pytest
+from psutil.tests import reload_module
+from psutil.tests import retry_on_failure
+from psutil.tests import safe_rmpath
+from psutil.tests import sh
+from psutil.tests import skip_on_not_implemented
+from psutil.tests import which
+
+
+if LINUX:
+    from psutil._pslinux import CLOCK_TICKS
+    from psutil._pslinux import RootFsDeviceFinder
+    from psutil._pslinux import calculate_avail_vmem
+    from psutil._pslinux import open_binary
+
+
+HERE = os.path.abspath(os.path.dirname(__file__))
+SIOCGIFADDR = 0x8915
+SIOCGIFHWADDR = 0x8927
+SIOCGIFNETMASK = 0x891B
+SIOCGIFBRDADDR = 0x8919
+if LINUX:
+    SECTOR_SIZE = 512
+# =====================================================================
+# --- utils
+# =====================================================================
+
+
+def get_ipv4_address(ifname):
+    import fcntl
+
+    ifname = ifname[:15]
+    if PY3:
+        ifname = bytes(ifname, 'ascii')
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    with contextlib.closing(s):
+        return socket.inet_ntoa(
+            fcntl.ioctl(s.fileno(), SIOCGIFADDR, struct.pack('256s', ifname))[
+                20:24
+            ]
+        )
+
+
+def get_ipv4_netmask(ifname):
+    import fcntl
+
+    ifname = ifname[:15]
+    if PY3:
+        ifname = bytes(ifname, 'ascii')
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    with contextlib.closing(s):
+        return socket.inet_ntoa(
+            fcntl.ioctl(
+                s.fileno(), SIOCGIFNETMASK, struct.pack('256s', ifname)
+            )[20:24]
+        )
+
+
+def get_ipv4_broadcast(ifname):
+    import fcntl
+
+    ifname = ifname[:15]
+    if PY3:
+        ifname = bytes(ifname, 'ascii')
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    with contextlib.closing(s):
+        return socket.inet_ntoa(
+            fcntl.ioctl(
+                s.fileno(), SIOCGIFBRDADDR, struct.pack('256s', ifname)
+            )[20:24]
+        )
+
+
+def get_ipv6_addresses(ifname):
+    with open("/proc/net/if_inet6") as f:
+        all_fields = []
+        for line in f:
+            fields = line.split()
+            if fields[-1] == ifname:
+                all_fields.append(fields)
+
+        if len(all_fields) == 0:
+            raise ValueError("could not find interface %r" % ifname)
+
+    for i in range(len(all_fields)):
+        unformatted = all_fields[i][0]
+        groups = []
+        for j in range(0, len(unformatted), 4):
+            groups.append(unformatted[j : j + 4])
+        formatted = ":".join(groups)
+        packed = socket.inet_pton(socket.AF_INET6, formatted)
+        all_fields[i] = socket.inet_ntop(socket.AF_INET6, packed)
+    return all_fields
+
+
+def get_mac_address(ifname):
+    import fcntl
+
+    ifname = ifname[:15]
+    if PY3:
+        ifname = bytes(ifname, 'ascii')
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    with contextlib.closing(s):
+        info = fcntl.ioctl(
+            s.fileno(), SIOCGIFHWADDR, struct.pack('256s', ifname)
+        )
+        if PY3:
+
+            def ord(x):
+                return x
+
+        else:
+            import __builtin__
+
+            ord = __builtin__.ord
+        return ''.join(['%02x:' % ord(char) for char in info[18:24]])[:-1]
+
+
+def free_swap():
+    """Parse 'free' cmd and return swap memory's s total, used and free
+    values.
+    """
+    out = sh(["free", "-b"], env={"LANG": "C.UTF-8"})
+    lines = out.split('\n')
+    for line in lines:
+        if line.startswith('Swap'):
+            _, total, used, free = line.split()
+            nt = collections.namedtuple('free', 'total used free')
+            return nt(int(total), int(used), int(free))
+    raise ValueError(
+        "can't find 'Swap' in 'free' output:\n%s" % '\n'.join(lines)
+    )
+
+
+def free_physmem():
+    """Parse 'free' cmd and return physical memory's total, used
+    and free values.
+    """
+    # Note: free can have 2 different formats, invalidating 'shared'
+    # and 'cached' memory which may have different positions so we
+    # do not return them.
+    # https://github.com/giampaolo/psutil/issues/538#issuecomment-57059946
+    out = sh(["free", "-b"], env={"LANG": "C.UTF-8"})
+    lines = out.split('\n')
+    for line in lines:
+        if line.startswith('Mem'):
+            total, used, free, shared = (int(x) for x in line.split()[1:5])
+            nt = collections.namedtuple(
+                'free', 'total used free shared output'
+            )
+            return nt(total, used, free, shared, out)
+    raise ValueError(
+        "can't find 'Mem' in 'free' output:\n%s" % '\n'.join(lines)
+    )
+
+
+def vmstat(stat):
+    out = sh(["vmstat", "-s"], env={"LANG": "C.UTF-8"})
+    for line in out.split("\n"):
+        line = line.strip()
+        if stat in line:
+            return int(line.split(' ')[0])
+    raise ValueError("can't find %r in 'vmstat' output" % stat)
+
+
+def get_free_version_info():
+    out = sh(["free", "-V"]).strip()
+    if 'UNKNOWN' in out:
+        raise pytest.skip("can't determine free version")
+    return tuple(map(int, re.findall(r'\d+', out.split()[-1])))
+
+
+@contextlib.contextmanager
+def mock_open_content(pairs):
+    """Mock open() builtin and forces it to return a certain content
+    for a given path. `pairs` is a {"path": "content", ...} dict.
+    """
+
+    def open_mock(name, *args, **kwargs):
+        if name in pairs:
+            content = pairs[name]
+            if PY3:
+                if isinstance(content, basestring):
+                    return io.StringIO(content)
+                else:
+                    return io.BytesIO(content)
+            else:
+                return io.BytesIO(content)
+        else:
+            return orig_open(name, *args, **kwargs)
+
+    orig_open = open
+    patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+    with mock.patch(patch_point, create=True, side_effect=open_mock) as m:
+        yield m
+
+
+@contextlib.contextmanager
+def mock_open_exception(for_path, exc):
+    """Mock open() builtin and raises `exc` if the path being opened
+    matches `for_path`.
+    """
+
+    def open_mock(name, *args, **kwargs):
+        if name == for_path:
+            raise exc
+        else:
+            return orig_open(name, *args, **kwargs)
+
+    orig_open = open
+    patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+    with mock.patch(patch_point, create=True, side_effect=open_mock) as m:
+        yield m
+
+
+# =====================================================================
+# --- system virtual memory
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemVirtualMemoryAgainstFree(PsutilTestCase):
+    def test_total(self):
+        cli_value = free_physmem().total
+        psutil_value = psutil.virtual_memory().total
+        assert cli_value == psutil_value
+
+    @retry_on_failure()
+    def test_used(self):
+        # Older versions of procps used slab memory to calculate used memory.
+        # This got changed in:
+        # https://gitlab.com/procps-ng/procps/commit/
+        #     05d751c4f076a2f0118b914c5e51cfbb4762ad8e
+        # Newer versions of procps are using yet another way to compute used
+        # memory.
+        # https://gitlab.com/procps-ng/procps/commit/
+        #     2184e90d2e7cdb582f9a5b706b47015e56707e4d
+        if get_free_version_info() < (3, 3, 12):
+            raise pytest.skip("free version too old")
+        if get_free_version_info() >= (4, 0, 0):
+            raise pytest.skip("free version too recent")
+        cli_value = free_physmem().used
+        psutil_value = psutil.virtual_memory().used
+        assert abs(cli_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_free(self):
+        cli_value = free_physmem().free
+        psutil_value = psutil.virtual_memory().free
+        assert abs(cli_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_shared(self):
+        free = free_physmem()
+        free_value = free.shared
+        if free_value == 0:
+            raise pytest.skip("free does not support 'shared' column")
+        psutil_value = psutil.virtual_memory().shared
+        assert (
+            abs(free_value - psutil_value) < TOLERANCE_SYS_MEM
+        ), '%s %s \n%s' % (free_value, psutil_value, free.output)
+
+    @retry_on_failure()
+    def test_available(self):
+        # "free" output format has changed at some point:
+        # https://github.com/giampaolo/psutil/issues/538#issuecomment-147192098
+        out = sh(["free", "-b"])
+        lines = out.split('\n')
+        if 'available' not in lines[0]:
+            raise pytest.skip("free does not support 'available' column")
+        else:
+            free_value = int(lines[1].split()[-1])
+            psutil_value = psutil.virtual_memory().available
+            assert (
+                abs(free_value - psutil_value) < TOLERANCE_SYS_MEM
+            ), '%s %s \n%s' % (free_value, psutil_value, out)
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemVirtualMemoryAgainstVmstat(PsutilTestCase):
+    def test_total(self):
+        vmstat_value = vmstat('total memory') * 1024
+        psutil_value = psutil.virtual_memory().total
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_used(self):
+        # Older versions of procps used slab memory to calculate used memory.
+        # This got changed in:
+        # https://gitlab.com/procps-ng/procps/commit/
+        #     05d751c4f076a2f0118b914c5e51cfbb4762ad8e
+        # Newer versions of procps are using yet another way to compute used
+        # memory.
+        # https://gitlab.com/procps-ng/procps/commit/
+        #     2184e90d2e7cdb582f9a5b706b47015e56707e4d
+        if get_free_version_info() < (3, 3, 12):
+            raise pytest.skip("free version too old")
+        if get_free_version_info() >= (4, 0, 0):
+            raise pytest.skip("free version too recent")
+        vmstat_value = vmstat('used memory') * 1024
+        psutil_value = psutil.virtual_memory().used
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_free(self):
+        vmstat_value = vmstat('free memory') * 1024
+        psutil_value = psutil.virtual_memory().free
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_buffers(self):
+        vmstat_value = vmstat('buffer memory') * 1024
+        psutil_value = psutil.virtual_memory().buffers
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_active(self):
+        vmstat_value = vmstat('active memory') * 1024
+        psutil_value = psutil.virtual_memory().active
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_inactive(self):
+        vmstat_value = vmstat('inactive memory') * 1024
+        psutil_value = psutil.virtual_memory().inactive
+        assert abs(vmstat_value - psutil_value) < TOLERANCE_SYS_MEM
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemVirtualMemoryMocks(PsutilTestCase):
+    def test_warnings_on_misses(self):
+        # Emulate a case where /proc/meminfo provides few info.
+        # psutil is supposed to set the missing fields to 0 and
+        # raise a warning.
+        content = textwrap.dedent("""\
+            Active(anon):    6145416 kB
+            Active(file):    2950064 kB
+            Inactive(anon):   574764 kB
+            Inactive(file):  1567648 kB
+            MemAvailable:         -1 kB
+            MemFree:         2057400 kB
+            MemTotal:       16325648 kB
+            SReclaimable:     346648 kB
+            """).encode()
+        with mock_open_content({'/proc/meminfo': content}) as m:
+            with warnings.catch_warnings(record=True) as ws:
+                warnings.simplefilter("always")
+                ret = psutil.virtual_memory()
+                assert m.called
+                assert len(ws) == 1
+                w = ws[0]
+                assert "memory stats couldn't be determined" in str(w.message)
+                assert "cached" in str(w.message)
+                assert "shared" in str(w.message)
+                assert "active" in str(w.message)
+                assert "inactive" in str(w.message)
+                assert "buffers" in str(w.message)
+                assert "available" in str(w.message)
+                assert ret.cached == 0
+                assert ret.active == 0
+                assert ret.inactive == 0
+                assert ret.shared == 0
+                assert ret.buffers == 0
+                assert ret.available == 0
+                assert ret.slab == 0
+
+    @retry_on_failure()
+    def test_avail_old_percent(self):
+        # Make sure that our calculation of avail mem for old kernels
+        # is off by max 15%.
+        mems = {}
+        with open_binary('/proc/meminfo') as f:
+            for line in f:
+                fields = line.split()
+                mems[fields[0]] = int(fields[1]) * 1024
+
+        a = calculate_avail_vmem(mems)
+        if b'MemAvailable:' in mems:
+            b = mems[b'MemAvailable:']
+            diff_percent = abs(a - b) / a * 100
+            assert diff_percent < 15
+
+    def test_avail_old_comes_from_kernel(self):
+        # Make sure "MemAvailable:" coluimn is used instead of relying
+        # on our internal algorithm to calculate avail mem.
+        content = textwrap.dedent("""\
+            Active:          9444728 kB
+            Active(anon):    6145416 kB
+            Active(file):    2950064 kB
+            Buffers:          287952 kB
+            Cached:          4818144 kB
+            Inactive(file):  1578132 kB
+            Inactive(anon):   574764 kB
+            Inactive(file):  1567648 kB
+            MemAvailable:    6574984 kB
+            MemFree:         2057400 kB
+            MemTotal:       16325648 kB
+            Shmem:            577588 kB
+            SReclaimable:     346648 kB
+            """).encode()
+        with mock_open_content({'/proc/meminfo': content}) as m:
+            with warnings.catch_warnings(record=True) as ws:
+                ret = psutil.virtual_memory()
+            assert m.called
+            assert ret.available == 6574984 * 1024
+            w = ws[0]
+            assert "inactive memory stats couldn't be determined" in str(
+                w.message
+            )
+
+    def test_avail_old_missing_fields(self):
+        # Remove Active(file), Inactive(file) and SReclaimable
+        # from /proc/meminfo and make sure the fallback is used
+        # (free + cached),
+        content = textwrap.dedent("""\
+            Active:          9444728 kB
+            Active(anon):    6145416 kB
+            Buffers:          287952 kB
+            Cached:          4818144 kB
+            Inactive(file):  1578132 kB
+            Inactive(anon):   574764 kB
+            MemFree:         2057400 kB
+            MemTotal:       16325648 kB
+            Shmem:            577588 kB
+            """).encode()
+        with mock_open_content({"/proc/meminfo": content}) as m:
+            with warnings.catch_warnings(record=True) as ws:
+                ret = psutil.virtual_memory()
+            assert m.called
+            assert ret.available == 2057400 * 1024 + 4818144 * 1024
+            w = ws[0]
+            assert "inactive memory stats couldn't be determined" in str(
+                w.message
+            )
+
+    def test_avail_old_missing_zoneinfo(self):
+        # Remove /proc/zoneinfo file. Make sure fallback is used
+        # (free + cached).
+        content = textwrap.dedent("""\
+            Active:          9444728 kB
+            Active(anon):    6145416 kB
+            Active(file):    2950064 kB
+            Buffers:          287952 kB
+            Cached:          4818144 kB
+            Inactive(file):  1578132 kB
+            Inactive(anon):   574764 kB
+            Inactive(file):  1567648 kB
+            MemFree:         2057400 kB
+            MemTotal:       16325648 kB
+            Shmem:            577588 kB
+            SReclaimable:     346648 kB
+            """).encode()
+        with mock_open_content({"/proc/meminfo": content}):
+            with mock_open_exception(
+                "/proc/zoneinfo",
+                IOError(errno.ENOENT, 'no such file or directory'),
+            ):
+                with warnings.catch_warnings(record=True) as ws:
+                    ret = psutil.virtual_memory()
+                    assert ret.available == 2057400 * 1024 + 4818144 * 1024
+                    w = ws[0]
+                    assert (
+                        "inactive memory stats couldn't be determined"
+                        in str(w.message)
+                    )
+
+    def test_virtual_memory_mocked(self):
+        # Emulate /proc/meminfo because neither vmstat nor free return slab.
+        content = textwrap.dedent("""\
+            MemTotal:              100 kB
+            MemFree:               2 kB
+            MemAvailable:          3 kB
+            Buffers:               4 kB
+            Cached:                5 kB
+            SwapCached:            6 kB
+            Active:                7 kB
+            Inactive:              8 kB
+            Active(anon):          9 kB
+            Inactive(anon):        10 kB
+            Active(file):          11 kB
+            Inactive(file):        12 kB
+            Unevictable:           13 kB
+            Mlocked:               14 kB
+            SwapTotal:             15 kB
+            SwapFree:              16 kB
+            Dirty:                 17 kB
+            Writeback:             18 kB
+            AnonPages:             19 kB
+            Mapped:                20 kB
+            Shmem:                 21 kB
+            Slab:                  22 kB
+            SReclaimable:          23 kB
+            SUnreclaim:            24 kB
+            KernelStack:           25 kB
+            PageTables:            26 kB
+            NFS_Unstable:          27 kB
+            Bounce:                28 kB
+            WritebackTmp:          29 kB
+            CommitLimit:           30 kB
+            Committed_AS:          31 kB
+            VmallocTotal:          32 kB
+            VmallocUsed:           33 kB
+            VmallocChunk:          34 kB
+            HardwareCorrupted:     35 kB
+            AnonHugePages:         36 kB
+            ShmemHugePages:        37 kB
+            ShmemPmdMapped:        38 kB
+            CmaTotal:              39 kB
+            CmaFree:               40 kB
+            HugePages_Total:       41 kB
+            HugePages_Free:        42 kB
+            HugePages_Rsvd:        43 kB
+            HugePages_Surp:        44 kB
+            Hugepagesize:          45 kB
+            DirectMap46k:          46 kB
+            DirectMap47M:          47 kB
+            DirectMap48G:          48 kB
+            """).encode()
+        with mock_open_content({"/proc/meminfo": content}) as m:
+            mem = psutil.virtual_memory()
+            assert m.called
+            assert mem.total == 100 * 1024
+            assert mem.free == 2 * 1024
+            assert mem.buffers == 4 * 1024
+            # cached mem also includes reclaimable memory
+            assert mem.cached == (5 + 23) * 1024
+            assert mem.shared == 21 * 1024
+            assert mem.active == 7 * 1024
+            assert mem.inactive == 8 * 1024
+            assert mem.slab == 22 * 1024
+            assert mem.available == 3 * 1024
+
+
+# =====================================================================
+# --- system swap memory
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemSwapMemory(PsutilTestCase):
+    @staticmethod
+    def meminfo_has_swap_info():
+        """Return True if /proc/meminfo provides swap metrics."""
+        with open("/proc/meminfo") as f:
+            data = f.read()
+        return 'SwapTotal:' in data and 'SwapFree:' in data
+
+    def test_total(self):
+        free_value = free_swap().total
+        psutil_value = psutil.swap_memory().total
+        assert abs(free_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_used(self):
+        free_value = free_swap().used
+        psutil_value = psutil.swap_memory().used
+        assert abs(free_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    @retry_on_failure()
+    def test_free(self):
+        free_value = free_swap().free
+        psutil_value = psutil.swap_memory().free
+        assert abs(free_value - psutil_value) < TOLERANCE_SYS_MEM
+
+    def test_missing_sin_sout(self):
+        with mock.patch('psutil._common.open', create=True) as m:
+            with warnings.catch_warnings(record=True) as ws:
+                warnings.simplefilter("always")
+                ret = psutil.swap_memory()
+                assert m.called
+                assert len(ws) == 1
+                w = ws[0]
+                assert (
+                    "'sin' and 'sout' swap memory stats couldn't be determined"
+                    in str(w.message)
+                )
+                assert ret.sin == 0
+                assert ret.sout == 0
+
+    def test_no_vmstat_mocked(self):
+        # see https://github.com/giampaolo/psutil/issues/722
+        with mock_open_exception(
+            "/proc/vmstat", IOError(errno.ENOENT, 'no such file or directory')
+        ) as m:
+            with warnings.catch_warnings(record=True) as ws:
+                warnings.simplefilter("always")
+                ret = psutil.swap_memory()
+                assert m.called
+                assert len(ws) == 1
+                w = ws[0]
+                assert (
+                    "'sin' and 'sout' swap memory stats couldn't "
+                    "be determined and were set to 0"
+                    in str(w.message)
+                )
+                assert ret.sin == 0
+                assert ret.sout == 0
+
+    def test_meminfo_against_sysinfo(self):
+        # Make sure the content of /proc/meminfo about swap memory
+        # matches sysinfo() syscall, see:
+        # https://github.com/giampaolo/psutil/issues/1015
+        if not self.meminfo_has_swap_info():
+            raise pytest.skip("/proc/meminfo has no swap metrics")
+        with mock.patch('psutil._pslinux.cext.linux_sysinfo') as m:
+            swap = psutil.swap_memory()
+        assert not m.called
+        import psutil._psutil_linux as cext
+
+        _, _, _, _, total, free, unit_multiplier = cext.linux_sysinfo()
+        total *= unit_multiplier
+        free *= unit_multiplier
+        assert swap.total == total
+        assert abs(swap.free - free) < TOLERANCE_SYS_MEM
+
+    def test_emulate_meminfo_has_no_metrics(self):
+        # Emulate a case where /proc/meminfo provides no swap metrics
+        # in which case sysinfo() syscall is supposed to be used
+        # as a fallback.
+        with mock_open_content({"/proc/meminfo": b""}) as m:
+            psutil.swap_memory()
+            assert m.called
+
+
+# =====================================================================
+# --- system CPU
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemCPUTimes(PsutilTestCase):
+    def test_fields(self):
+        fields = psutil.cpu_times()._fields
+        kernel_ver = re.findall(r'\d+\.\d+\.\d+', os.uname()[2])[0]
+        kernel_ver_info = tuple(map(int, kernel_ver.split('.')))
+        if kernel_ver_info >= (2, 6, 11):
+            assert 'steal' in fields
+        else:
+            assert 'steal' not in fields
+        if kernel_ver_info >= (2, 6, 24):
+            assert 'guest' in fields
+        else:
+            assert 'guest' not in fields
+        if kernel_ver_info >= (3, 2, 0):
+            assert 'guest_nice' in fields
+        else:
+            assert 'guest_nice' not in fields
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemCPUCountLogical(PsutilTestCase):
+    @pytest.mark.skipif(
+        not os.path.exists("/sys/devices/system/cpu/online"),
+        reason="/sys/devices/system/cpu/online does not exist",
+    )
+    def test_against_sysdev_cpu_online(self):
+        with open("/sys/devices/system/cpu/online") as f:
+            value = f.read().strip()
+        if "-" in str(value):
+            value = int(value.split('-')[1]) + 1
+            assert psutil.cpu_count() == value
+
+    @pytest.mark.skipif(
+        not os.path.exists("/sys/devices/system/cpu"),
+        reason="/sys/devices/system/cpu does not exist",
+    )
+    def test_against_sysdev_cpu_num(self):
+        ls = os.listdir("/sys/devices/system/cpu")
+        count = len([x for x in ls if re.search(r"cpu\d+$", x) is not None])
+        assert psutil.cpu_count() == count
+
+    @pytest.mark.skipif(
+        not which("nproc"), reason="nproc utility not available"
+    )
+    def test_against_nproc(self):
+        num = int(sh("nproc --all"))
+        assert psutil.cpu_count(logical=True) == num
+
+    @pytest.mark.skipif(
+        not which("lscpu"), reason="lscpu utility not available"
+    )
+    def test_against_lscpu(self):
+        out = sh("lscpu -p")
+        num = len([x for x in out.split('\n') if not x.startswith('#')])
+        assert psutil.cpu_count(logical=True) == num
+
+    def test_emulate_fallbacks(self):
+        import psutil._pslinux
+
+        original = psutil._pslinux.cpu_count_logical()
+        # Here we want to mock os.sysconf("SC_NPROCESSORS_ONLN") in
+        # order to cause the parsing of /proc/cpuinfo and /proc/stat.
+        with mock.patch(
+            'psutil._pslinux.os.sysconf', side_effect=ValueError
+        ) as m:
+            assert psutil._pslinux.cpu_count_logical() == original
+            assert m.called
+
+            # Let's have open() return empty data and make sure None is
+            # returned ('cause we mimic os.cpu_count()).
+            with mock.patch('psutil._common.open', create=True) as m:
+                assert psutil._pslinux.cpu_count_logical() is None
+                assert m.call_count == 2
+                # /proc/stat should be the last one
+                assert m.call_args[0][0] == '/proc/stat'
+
+            # Let's push this a bit further and make sure /proc/cpuinfo
+            # parsing works as expected.
+            with open('/proc/cpuinfo', 'rb') as f:
+                cpuinfo_data = f.read()
+            fake_file = io.BytesIO(cpuinfo_data)
+            with mock.patch(
+                'psutil._common.open', return_value=fake_file, create=True
+            ) as m:
+                assert psutil._pslinux.cpu_count_logical() == original
+
+            # Finally, let's make /proc/cpuinfo return meaningless data;
+            # this way we'll fall back on relying on /proc/stat
+            with mock_open_content({"/proc/cpuinfo": b""}) as m:
+                assert psutil._pslinux.cpu_count_logical() == original
+                assert m.called
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemCPUCountCores(PsutilTestCase):
+    @pytest.mark.skipif(
+        not which("lscpu"), reason="lscpu utility not available"
+    )
+    def test_against_lscpu(self):
+        out = sh("lscpu -p")
+        core_ids = set()
+        for line in out.split('\n'):
+            if not line.startswith('#'):
+                fields = line.split(',')
+                core_ids.add(fields[1])
+        assert psutil.cpu_count(logical=False) == len(core_ids)
+
+    def test_method_2(self):
+        meth_1 = psutil._pslinux.cpu_count_cores()
+        with mock.patch('glob.glob', return_value=[]) as m:
+            meth_2 = psutil._pslinux.cpu_count_cores()
+            assert m.called
+        if meth_1 is not None:
+            assert meth_1 == meth_2
+
+    def test_emulate_none(self):
+        with mock.patch('glob.glob', return_value=[]) as m1:
+            with mock.patch('psutil._common.open', create=True) as m2:
+                assert psutil._pslinux.cpu_count_cores() is None
+        assert m1.called
+        assert m2.called
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemCPUFrequency(PsutilTestCase):
+    @pytest.mark.skipif(not HAS_CPU_FREQ, reason="not supported")
+    def test_emulate_use_second_file(self):
+        # https://github.com/giampaolo/psutil/issues/981
+        def path_exists_mock(path):
+            if path.startswith("/sys/devices/system/cpu/cpufreq/policy"):
+                return False
+            else:
+                return orig_exists(path)
+
+        orig_exists = os.path.exists
+        with mock.patch(
+            "os.path.exists", side_effect=path_exists_mock, create=True
+        ):
+            assert psutil.cpu_freq()
+
+    @pytest.mark.skipif(not HAS_CPU_FREQ, reason="not supported")
+    @pytest.mark.skipif(
+        AARCH64, reason="aarch64 does not report mhz in /proc/cpuinfo"
+    )
+    def test_emulate_use_cpuinfo(self):
+        # Emulate a case where /sys/devices/system/cpu/cpufreq* does not
+        # exist and /proc/cpuinfo is used instead.
+        def path_exists_mock(path):
+            if path.startswith('/sys/devices/system/cpu/'):
+                return False
+            else:
+                return os_path_exists(path)
+
+        os_path_exists = os.path.exists
+        try:
+            with mock.patch("os.path.exists", side_effect=path_exists_mock):
+                reload_module(psutil._pslinux)
+                ret = psutil.cpu_freq()
+                assert ret, ret
+                assert ret.max == 0.0
+                assert ret.min == 0.0
+                for freq in psutil.cpu_freq(percpu=True):
+                    assert freq.max == 0.0
+                    assert freq.min == 0.0
+        finally:
+            reload_module(psutil._pslinux)
+            reload_module(psutil)
+
+    @pytest.mark.skipif(not HAS_CPU_FREQ, reason="not supported")
+    def test_emulate_data(self):
+        def open_mock(name, *args, **kwargs):
+            if name.endswith('/scaling_cur_freq') and name.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy"
+            ):
+                return io.BytesIO(b"500000")
+            elif name.endswith('/scaling_min_freq') and name.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy"
+            ):
+                return io.BytesIO(b"600000")
+            elif name.endswith('/scaling_max_freq') and name.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy"
+            ):
+                return io.BytesIO(b"700000")
+            elif name == '/proc/cpuinfo':
+                return io.BytesIO(b"cpu MHz     : 500")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            with mock.patch('os.path.exists', return_value=True):
+                freq = psutil.cpu_freq()
+                assert freq.current == 500.0
+                # when /proc/cpuinfo is used min and max frequencies are not
+                # available and are set to 0.
+                if freq.min != 0.0:
+                    assert freq.min == 600.0
+                if freq.max != 0.0:
+                    assert freq.max == 700.0
+
+    @pytest.mark.skipif(not HAS_CPU_FREQ, reason="not supported")
+    def test_emulate_multi_cpu(self):
+        def open_mock(name, *args, **kwargs):
+            n = name
+            if n.endswith('/scaling_cur_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy0"
+            ):
+                return io.BytesIO(b"100000")
+            elif n.endswith('/scaling_min_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy0"
+            ):
+                return io.BytesIO(b"200000")
+            elif n.endswith('/scaling_max_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy0"
+            ):
+                return io.BytesIO(b"300000")
+            elif n.endswith('/scaling_cur_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy1"
+            ):
+                return io.BytesIO(b"400000")
+            elif n.endswith('/scaling_min_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy1"
+            ):
+                return io.BytesIO(b"500000")
+            elif n.endswith('/scaling_max_freq') and n.startswith(
+                "/sys/devices/system/cpu/cpufreq/policy1"
+            ):
+                return io.BytesIO(b"600000")
+            elif name == '/proc/cpuinfo':
+                return io.BytesIO(b"cpu MHz     : 100\ncpu MHz     : 400")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            with mock.patch('os.path.exists', return_value=True):
+                with mock.patch(
+                    'psutil._pslinux.cpu_count_logical', return_value=2
+                ):
+                    freq = psutil.cpu_freq(percpu=True)
+                    assert freq[0].current == 100.0
+                    if freq[0].min != 0.0:
+                        assert freq[0].min == 200.0
+                    if freq[0].max != 0.0:
+                        assert freq[0].max == 300.0
+                    assert freq[1].current == 400.0
+                    if freq[1].min != 0.0:
+                        assert freq[1].min == 500.0
+                    if freq[1].max != 0.0:
+                        assert freq[1].max == 600.0
+
+    @pytest.mark.skipif(not HAS_CPU_FREQ, reason="not supported")
+    def test_emulate_no_scaling_cur_freq_file(self):
+        # See: https://github.com/giampaolo/psutil/issues/1071
+        def open_mock(name, *args, **kwargs):
+            if name.endswith('/scaling_cur_freq'):
+                raise IOError(errno.ENOENT, "")
+            elif name.endswith('/cpuinfo_cur_freq'):
+                return io.BytesIO(b"200000")
+            elif name == '/proc/cpuinfo':
+                return io.BytesIO(b"cpu MHz     : 200")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            with mock.patch('os.path.exists', return_value=True):
+                with mock.patch(
+                    'psutil._pslinux.cpu_count_logical', return_value=1
+                ):
+                    freq = psutil.cpu_freq()
+                    assert freq.current == 200
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemCPUStats(PsutilTestCase):
+
+    # XXX: fails too often.
+    # def test_ctx_switches(self):
+    #     vmstat_value = vmstat("context switches")
+    #     psutil_value = psutil.cpu_stats().ctx_switches
+    #     self.assertAlmostEqual(vmstat_value, psutil_value, delta=500)
+
+    def test_interrupts(self):
+        vmstat_value = vmstat("interrupts")
+        psutil_value = psutil.cpu_stats().interrupts
+        assert abs(vmstat_value - psutil_value) < 500
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestLoadAvg(PsutilTestCase):
+    @pytest.mark.skipif(not HAS_GETLOADAVG, reason="not supported")
+    def test_getloadavg(self):
+        psutil_value = psutil.getloadavg()
+        with open("/proc/loadavg") as f:
+            proc_value = f.read().split()
+
+        assert abs(float(proc_value[0]) - psutil_value[0]) < 1
+        assert abs(float(proc_value[1]) - psutil_value[1]) < 1
+        assert abs(float(proc_value[2]) - psutil_value[2]) < 1
+
+
+# =====================================================================
+# --- system network
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemNetIfAddrs(PsutilTestCase):
+    def test_ips(self):
+        for name, addrs in psutil.net_if_addrs().items():
+            for addr in addrs:
+                if addr.family == psutil.AF_LINK:
+                    assert addr.address == get_mac_address(name)
+                elif addr.family == socket.AF_INET:
+                    assert addr.address == get_ipv4_address(name)
+                    assert addr.netmask == get_ipv4_netmask(name)
+                    if addr.broadcast is not None:
+                        assert addr.broadcast == get_ipv4_broadcast(name)
+                    else:
+                        assert get_ipv4_broadcast(name) == '0.0.0.0'
+                elif addr.family == socket.AF_INET6:
+                    # IPv6 addresses can have a percent symbol at the end.
+                    # E.g. these 2 are equivalent:
+                    # "fe80::1ff:fe23:4567:890a"
+                    # "fe80::1ff:fe23:4567:890a%eth0"
+                    # That is the "zone id" portion, which usually is the name
+                    # of the network interface.
+                    address = addr.address.split('%')[0]
+                    assert address in get_ipv6_addresses(name)
+
+    # XXX - not reliable when having virtual NICs installed by Docker.
+    # @pytest.mark.skipif(not which('ip'), reason="'ip' utility not available")
+    # def test_net_if_names(self):
+    #     out = sh("ip addr").strip()
+    #     nics = [x for x in psutil.net_if_addrs().keys() if ':' not in x]
+    #     found = 0
+    #     for line in out.split('\n'):
+    #         line = line.strip()
+    #         if re.search(r"^\d+:", line):
+    #             found += 1
+    #             name = line.split(':')[1].strip()
+    #             self.assertIn(name, nics)
+    #     self.assertEqual(len(nics), found, msg="%s\n---\n%s" % (
+    #         pprint.pformat(nics), out))
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+@pytest.mark.skipif(QEMU_USER, reason="QEMU user not supported")
+class TestSystemNetIfStats(PsutilTestCase):
+    @pytest.mark.skipif(
+        not which("ifconfig"), reason="ifconfig utility not available"
+    )
+    def test_against_ifconfig(self):
+        for name, stats in psutil.net_if_stats().items():
+            try:
+                out = sh("ifconfig %s" % name)
+            except RuntimeError:
+                pass
+            else:
+                assert stats.isup == ('RUNNING' in out), out
+                assert stats.mtu == int(
+                    re.findall(r'(?i)MTU[: ](\d+)', out)[0]
+                )
+
+    def test_mtu(self):
+        for name, stats in psutil.net_if_stats().items():
+            with open("/sys/class/net/%s/mtu" % name) as f:
+                assert stats.mtu == int(f.read().strip())
+
+    @pytest.mark.skipif(
+        not which("ifconfig"), reason="ifconfig utility not available"
+    )
+    def test_flags(self):
+        # first line looks like this:
+        # "eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500"
+        matches_found = 0
+        for name, stats in psutil.net_if_stats().items():
+            try:
+                out = sh("ifconfig %s" % name)
+            except RuntimeError:
+                pass
+            else:
+                match = re.search(r"flags=(\d+)?<(.*?)>", out)
+                if match and len(match.groups()) >= 2:
+                    matches_found += 1
+                    ifconfig_flags = set(match.group(2).lower().split(","))
+                    psutil_flags = set(stats.flags.split(","))
+                    assert ifconfig_flags == psutil_flags
+                else:
+                    # ifconfig has a different output on CentOS 6
+                    # let's try that
+                    match = re.search(r"(.*)  MTU:(\d+)  Metric:(\d+)", out)
+                    if match and len(match.groups()) >= 3:
+                        matches_found += 1
+                        ifconfig_flags = set(match.group(1).lower().split())
+                        psutil_flags = set(stats.flags.split(","))
+                        assert ifconfig_flags == psutil_flags
+
+        if not matches_found:
+            raise self.fail("no matches were found")
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemNetIOCounters(PsutilTestCase):
+    @pytest.mark.skipif(
+        not which("ifconfig"), reason="ifconfig utility not available"
+    )
+    @retry_on_failure()
+    def test_against_ifconfig(self):
+        def ifconfig(nic):
+            ret = {}
+            out = sh("ifconfig %s" % nic)
+            ret['packets_recv'] = int(
+                re.findall(r'RX packets[: ](\d+)', out)[0]
+            )
+            ret['packets_sent'] = int(
+                re.findall(r'TX packets[: ](\d+)', out)[0]
+            )
+            ret['errin'] = int(re.findall(r'errors[: ](\d+)', out)[0])
+            ret['errout'] = int(re.findall(r'errors[: ](\d+)', out)[1])
+            ret['dropin'] = int(re.findall(r'dropped[: ](\d+)', out)[0])
+            ret['dropout'] = int(re.findall(r'dropped[: ](\d+)', out)[1])
+            ret['bytes_recv'] = int(
+                re.findall(r'RX (?:packets \d+ +)?bytes[: ](\d+)', out)[0]
+            )
+            ret['bytes_sent'] = int(
+                re.findall(r'TX (?:packets \d+ +)?bytes[: ](\d+)', out)[0]
+            )
+            return ret
+
+        nio = psutil.net_io_counters(pernic=True, nowrap=False)
+        for name, stats in nio.items():
+            try:
+                ifconfig_ret = ifconfig(name)
+            except RuntimeError:
+                continue
+            assert (
+                abs(stats.bytes_recv - ifconfig_ret['bytes_recv']) < 1024 * 10
+            )
+            assert (
+                abs(stats.bytes_sent - ifconfig_ret['bytes_sent']) < 1024 * 10
+            )
+            assert (
+                abs(stats.packets_recv - ifconfig_ret['packets_recv']) < 1024
+            )
+            assert (
+                abs(stats.packets_sent - ifconfig_ret['packets_sent']) < 1024
+            )
+            assert abs(stats.errin - ifconfig_ret['errin']) < 10
+            assert abs(stats.errout - ifconfig_ret['errout']) < 10
+            assert abs(stats.dropin - ifconfig_ret['dropin']) < 10
+            assert abs(stats.dropout - ifconfig_ret['dropout']) < 10
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemNetConnections(PsutilTestCase):
+    @mock.patch('psutil._pslinux.socket.inet_ntop', side_effect=ValueError)
+    @mock.patch('psutil._pslinux.supports_ipv6', return_value=False)
+    def test_emulate_ipv6_unsupported(self, supports_ipv6, inet_ntop):
+        # see: https://github.com/giampaolo/psutil/issues/623
+        try:
+            s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+            self.addCleanup(s.close)
+            s.bind(("::1", 0))
+        except socket.error:
+            pass
+        psutil.net_connections(kind='inet6')
+
+    def test_emulate_unix(self):
+        content = textwrap.dedent("""\
+            0: 00000003 000 000 0001 03 462170 @/tmp/dbus-Qw2hMPIU3n
+            0: 00000003 000 000 0001 03 35010 @/tmp/dbus-tB2X8h69BQ
+            0: 00000003 000 000 0001 03 34424 @/tmp/dbus-cHy80Y8O
+            000000000000000000000000000000000000000000000000000000
+            """)
+        with mock_open_content({"/proc/net/unix": content}) as m:
+            psutil.net_connections(kind='unix')
+            assert m.called
+
+
+# =====================================================================
+# --- system disks
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemDiskPartitions(PsutilTestCase):
+    @pytest.mark.skipif(
+        not hasattr(os, 'statvfs'), reason="os.statvfs() not available"
+    )
+    @skip_on_not_implemented()
+    def test_against_df(self):
+        # test psutil.disk_usage() and psutil.disk_partitions()
+        # against "df -a"
+        def df(path):
+            out = sh('df -P -B 1 "%s"' % path).strip()
+            lines = out.split('\n')
+            lines.pop(0)
+            line = lines.pop(0)
+            dev, total, used, free = line.split()[:4]
+            if dev == 'none':
+                dev = ''
+            total, used, free = int(total), int(used), int(free)
+            return dev, total, used, free
+
+        for part in psutil.disk_partitions(all=False):
+            usage = psutil.disk_usage(part.mountpoint)
+            _, total, used, free = df(part.mountpoint)
+            assert usage.total == total
+            assert abs(usage.free - free) < TOLERANCE_DISK_USAGE
+            assert abs(usage.used - used) < TOLERANCE_DISK_USAGE
+
+    def test_zfs_fs(self):
+        # Test that ZFS partitions are returned.
+        with open("/proc/filesystems") as f:
+            data = f.read()
+        if 'zfs' in data:
+            for part in psutil.disk_partitions():
+                if part.fstype == 'zfs':
+                    return
+
+        # No ZFS partitions on this system. Let's fake one.
+        fake_file = io.StringIO(u"nodev\tzfs\n")
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m1:
+            with mock.patch(
+                'psutil._pslinux.cext.disk_partitions',
+                return_value=[('/dev/sdb3', '/', 'zfs', 'rw')],
+            ) as m2:
+                ret = psutil.disk_partitions()
+                assert m1.called
+                assert m2.called
+                assert ret
+                assert ret[0].fstype == 'zfs'
+
+    def test_emulate_realpath_fail(self):
+        # See: https://github.com/giampaolo/psutil/issues/1307
+        try:
+            with mock.patch(
+                'os.path.realpath', return_value='/non/existent'
+            ) as m:
+                with pytest.raises(FileNotFoundError):
+                    psutil.disk_partitions()
+                assert m.called
+        finally:
+            psutil.PROCFS_PATH = "/proc"
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSystemDiskIoCounters(PsutilTestCase):
+    def test_emulate_kernel_2_4(self):
+        # Tests /proc/diskstats parsing format for 2.4 kernels, see:
+        # https://github.com/giampaolo/psutil/issues/767
+        content = "   3     0   1 hda 2 3 4 5 6 7 8 9 10 11 12"
+        with mock_open_content({'/proc/diskstats': content}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device', return_value=True
+            ):
+                ret = psutil.disk_io_counters(nowrap=False)
+                assert ret.read_count == 1
+                assert ret.read_merged_count == 2
+                assert ret.read_bytes == 3 * SECTOR_SIZE
+                assert ret.read_time == 4
+                assert ret.write_count == 5
+                assert ret.write_merged_count == 6
+                assert ret.write_bytes == 7 * SECTOR_SIZE
+                assert ret.write_time == 8
+                assert ret.busy_time == 10
+
+    def test_emulate_kernel_2_6_full(self):
+        # Tests /proc/diskstats parsing format for 2.6 kernels,
+        # lines reporting all metrics:
+        # https://github.com/giampaolo/psutil/issues/767
+        content = "   3    0   hda 1 2 3 4 5 6 7 8 9 10 11"
+        with mock_open_content({"/proc/diskstats": content}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device', return_value=True
+            ):
+                ret = psutil.disk_io_counters(nowrap=False)
+                assert ret.read_count == 1
+                assert ret.read_merged_count == 2
+                assert ret.read_bytes == 3 * SECTOR_SIZE
+                assert ret.read_time == 4
+                assert ret.write_count == 5
+                assert ret.write_merged_count == 6
+                assert ret.write_bytes == 7 * SECTOR_SIZE
+                assert ret.write_time == 8
+                assert ret.busy_time == 10
+
+    def test_emulate_kernel_2_6_limited(self):
+        # Tests /proc/diskstats parsing format for 2.6 kernels,
+        # where one line of /proc/partitions return a limited
+        # amount of metrics when it bumps into a partition
+        # (instead of a disk). See:
+        # https://github.com/giampaolo/psutil/issues/767
+        with mock_open_content({"/proc/diskstats": "   3    1   hda 1 2 3 4"}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device', return_value=True
+            ):
+                ret = psutil.disk_io_counters(nowrap=False)
+                assert ret.read_count == 1
+                assert ret.read_bytes == 2 * SECTOR_SIZE
+                assert ret.write_count == 3
+                assert ret.write_bytes == 4 * SECTOR_SIZE
+
+                assert ret.read_merged_count == 0
+                assert ret.read_time == 0
+                assert ret.write_merged_count == 0
+                assert ret.write_time == 0
+                assert ret.busy_time == 0
+
+    def test_emulate_include_partitions(self):
+        # Make sure that when perdisk=True disk partitions are returned,
+        # see:
+        # https://github.com/giampaolo/psutil/pull/1313#issuecomment-408626842
+        content = textwrap.dedent("""\
+            3    0   nvme0n1 1 2 3 4 5 6 7 8 9 10 11
+            3    0   nvme0n1p1 1 2 3 4 5 6 7 8 9 10 11
+            """)
+        with mock_open_content({"/proc/diskstats": content}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device', return_value=False
+            ):
+                ret = psutil.disk_io_counters(perdisk=True, nowrap=False)
+                assert len(ret) == 2
+                assert ret['nvme0n1'].read_count == 1
+                assert ret['nvme0n1p1'].read_count == 1
+                assert ret['nvme0n1'].write_count == 5
+                assert ret['nvme0n1p1'].write_count == 5
+
+    def test_emulate_exclude_partitions(self):
+        # Make sure that when perdisk=False partitions (e.g. 'sda1',
+        # 'nvme0n1p1') are skipped and not included in the total count.
+        # https://github.com/giampaolo/psutil/pull/1313#issuecomment-408626842
+        content = textwrap.dedent("""\
+            3    0   nvme0n1 1 2 3 4 5 6 7 8 9 10 11
+            3    0   nvme0n1p1 1 2 3 4 5 6 7 8 9 10 11
+            """)
+        with mock_open_content({"/proc/diskstats": content}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device', return_value=False
+            ):
+                ret = psutil.disk_io_counters(perdisk=False, nowrap=False)
+                assert ret is None
+
+        def is_storage_device(name):
+            return name == 'nvme0n1'
+
+        content = textwrap.dedent("""\
+            3    0   nvme0n1 1 2 3 4 5 6 7 8 9 10 11
+            3    0   nvme0n1p1 1 2 3 4 5 6 7 8 9 10 11
+            """)
+        with mock_open_content({"/proc/diskstats": content}):
+            with mock.patch(
+                'psutil._pslinux.is_storage_device',
+                create=True,
+                side_effect=is_storage_device,
+            ):
+                ret = psutil.disk_io_counters(perdisk=False, nowrap=False)
+                assert ret.read_count == 1
+                assert ret.write_count == 5
+
+    def test_emulate_use_sysfs(self):
+        def exists(path):
+            return path == '/proc/diskstats'
+
+        wprocfs = psutil.disk_io_counters(perdisk=True)
+        with mock.patch(
+            'psutil._pslinux.os.path.exists', create=True, side_effect=exists
+        ):
+            wsysfs = psutil.disk_io_counters(perdisk=True)
+        assert len(wprocfs) == len(wsysfs)
+
+    def test_emulate_not_impl(self):
+        def exists(path):
+            return False
+
+        with mock.patch(
+            'psutil._pslinux.os.path.exists', create=True, side_effect=exists
+        ):
+            with pytest.raises(NotImplementedError):
+                psutil.disk_io_counters()
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestRootFsDeviceFinder(PsutilTestCase):
+    def setUp(self):
+        dev = os.stat("/").st_dev
+        self.major = os.major(dev)
+        self.minor = os.minor(dev)
+
+    def test_call_methods(self):
+        finder = RootFsDeviceFinder()
+        if os.path.exists("/proc/partitions"):
+            finder.ask_proc_partitions()
+        else:
+            with pytest.raises(FileNotFoundError):
+                finder.ask_proc_partitions()
+        if os.path.exists(
+            "/sys/dev/block/%s:%s/uevent" % (self.major, self.minor)
+        ):
+            finder.ask_sys_dev_block()
+        else:
+            with pytest.raises(FileNotFoundError):
+                finder.ask_sys_dev_block()
+        finder.ask_sys_class_block()
+
+    @pytest.mark.skipif(GITHUB_ACTIONS, reason="unsupported on GITHUB_ACTIONS")
+    def test_comparisons(self):
+        finder = RootFsDeviceFinder()
+        assert finder.find() is not None
+
+        a = b = c = None
+        if os.path.exists("/proc/partitions"):
+            a = finder.ask_proc_partitions()
+        if os.path.exists(
+            "/sys/dev/block/%s:%s/uevent" % (self.major, self.minor)
+        ):
+            b = finder.ask_sys_class_block()
+        c = finder.ask_sys_dev_block()
+
+        base = a or b or c
+        if base and a:
+            assert base == a
+        if base and b:
+            assert base == b
+        if base and c:
+            assert base == c
+
+    @pytest.mark.skipif(
+        not which("findmnt"), reason="findmnt utility not available"
+    )
+    @pytest.mark.skipif(GITHUB_ACTIONS, reason="unsupported on GITHUB_ACTIONS")
+    def test_against_findmnt(self):
+        psutil_value = RootFsDeviceFinder().find()
+        findmnt_value = sh("findmnt -o SOURCE -rn /")
+        assert psutil_value == findmnt_value
+
+    def test_disk_partitions_mocked(self):
+        with mock.patch(
+            'psutil._pslinux.cext.disk_partitions',
+            return_value=[('/dev/root', '/', 'ext4', 'rw')],
+        ) as m:
+            part = psutil.disk_partitions()[0]
+            assert m.called
+            if not GITHUB_ACTIONS:
+                assert part.device != "/dev/root"
+                assert part.device == RootFsDeviceFinder().find()
+            else:
+                assert part.device == "/dev/root"
+
+
+# =====================================================================
+# --- misc
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestMisc(PsutilTestCase):
+    def test_boot_time(self):
+        vmstat_value = vmstat('boot time')
+        psutil_value = psutil.boot_time()
+        assert int(vmstat_value) == int(psutil_value)
+
+    def test_no_procfs_on_import(self):
+        my_procfs = self.get_testfn()
+        os.mkdir(my_procfs)
+
+        with open(os.path.join(my_procfs, 'stat'), 'w') as f:
+            f.write('cpu   0 0 0 0 0 0 0 0 0 0\n')
+            f.write('cpu0  0 0 0 0 0 0 0 0 0 0\n')
+            f.write('cpu1  0 0 0 0 0 0 0 0 0 0\n')
+
+        try:
+            orig_open = open
+
+            def open_mock(name, *args, **kwargs):
+                if name.startswith('/proc'):
+                    raise IOError(errno.ENOENT, 'rejecting access for test')
+                return orig_open(name, *args, **kwargs)
+
+            patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+            with mock.patch(patch_point, side_effect=open_mock):
+                reload_module(psutil)
+
+                with pytest.raises(IOError):
+                    psutil.cpu_times()
+                with pytest.raises(IOError):
+                    psutil.cpu_times(percpu=True)
+                with pytest.raises(IOError):
+                    psutil.cpu_percent()
+                with pytest.raises(IOError):
+                    psutil.cpu_percent(percpu=True)
+                with pytest.raises(IOError):
+                    psutil.cpu_times_percent()
+                with pytest.raises(IOError):
+                    psutil.cpu_times_percent(percpu=True)
+
+                psutil.PROCFS_PATH = my_procfs
+
+                assert psutil.cpu_percent() == 0
+                assert sum(psutil.cpu_times_percent()) == 0
+
+                # since we don't know the number of CPUs at import time,
+                # we awkwardly say there are none until the second call
+                per_cpu_percent = psutil.cpu_percent(percpu=True)
+                assert sum(per_cpu_percent) == 0
+
+                # ditto awkward length
+                per_cpu_times_percent = psutil.cpu_times_percent(percpu=True)
+                assert sum(map(sum, per_cpu_times_percent)) == 0
+
+                # much user, very busy
+                with open(os.path.join(my_procfs, 'stat'), 'w') as f:
+                    f.write('cpu   1 0 0 0 0 0 0 0 0 0\n')
+                    f.write('cpu0  1 0 0 0 0 0 0 0 0 0\n')
+                    f.write('cpu1  1 0 0 0 0 0 0 0 0 0\n')
+
+                assert psutil.cpu_percent() != 0
+                assert sum(psutil.cpu_percent(percpu=True)) != 0
+                assert sum(psutil.cpu_times_percent()) != 0
+                assert (
+                    sum(map(sum, psutil.cpu_times_percent(percpu=True))) != 0
+                )
+        finally:
+            shutil.rmtree(my_procfs)
+            reload_module(psutil)
+
+        assert psutil.PROCFS_PATH == '/proc'
+
+    def test_cpu_steal_decrease(self):
+        # Test cumulative cpu stats decrease. We should ignore this.
+        # See issue #1210.
+        content = textwrap.dedent("""\
+            cpu   0 0 0 0 0 0 0 1 0 0
+            cpu0  0 0 0 0 0 0 0 1 0 0
+            cpu1  0 0 0 0 0 0 0 1 0 0
+            """).encode()
+        with mock_open_content({"/proc/stat": content}) as m:
+            # first call to "percent" functions should read the new stat file
+            # and compare to the "real" file read at import time - so the
+            # values are meaningless
+            psutil.cpu_percent()
+            assert m.called
+            psutil.cpu_percent(percpu=True)
+            psutil.cpu_times_percent()
+            psutil.cpu_times_percent(percpu=True)
+
+        content = textwrap.dedent("""\
+            cpu   1 0 0 0 0 0 0 0 0 0
+            cpu0  1 0 0 0 0 0 0 0 0 0
+            cpu1  1 0 0 0 0 0 0 0 0 0
+            """).encode()
+        with mock_open_content({"/proc/stat": content}):
+            # Increase "user" while steal goes "backwards" to zero.
+            cpu_percent = psutil.cpu_percent()
+            assert m.called
+            cpu_percent_percpu = psutil.cpu_percent(percpu=True)
+            cpu_times_percent = psutil.cpu_times_percent()
+            cpu_times_percent_percpu = psutil.cpu_times_percent(percpu=True)
+            assert cpu_percent != 0
+            assert sum(cpu_percent_percpu) != 0
+            assert sum(cpu_times_percent) != 0
+            assert sum(cpu_times_percent) != 100.0
+            assert sum(map(sum, cpu_times_percent_percpu)) != 0
+            assert sum(map(sum, cpu_times_percent_percpu)) != 100.0
+            assert cpu_times_percent.steal == 0
+            assert cpu_times_percent.user != 0
+
+    def test_boot_time_mocked(self):
+        with mock.patch('psutil._common.open', create=True) as m:
+            with pytest.raises(RuntimeError):
+                psutil._pslinux.boot_time()
+            assert m.called
+
+    def test_users(self):
+        # Make sure the C extension converts ':0' and ':0.0' to
+        # 'localhost'.
+        for user in psutil.users():
+            assert user.host not in {":0", ":0.0"}
+
+    def test_procfs_path(self):
+        tdir = self.get_testfn()
+        os.mkdir(tdir)
+        try:
+            psutil.PROCFS_PATH = tdir
+            with pytest.raises(IOError):
+                psutil.virtual_memory()
+            with pytest.raises(IOError):
+                psutil.cpu_times()
+            with pytest.raises(IOError):
+                psutil.cpu_times(percpu=True)
+            with pytest.raises(IOError):
+                psutil.boot_time()
+            # self.assertRaises(IOError, psutil.pids)
+            with pytest.raises(IOError):
+                psutil.net_connections()
+            with pytest.raises(IOError):
+                psutil.net_io_counters()
+            with pytest.raises(IOError):
+                psutil.net_if_stats()
+            # self.assertRaises(IOError, psutil.disk_io_counters)
+            with pytest.raises(IOError):
+                psutil.disk_partitions()
+            with pytest.raises(psutil.NoSuchProcess):
+                psutil.Process()
+        finally:
+            psutil.PROCFS_PATH = "/proc"
+
+    @retry_on_failure()
+    @pytest.mark.skipif(PYTEST_PARALLEL, reason="skip if pytest-parallel")
+    def test_issue_687(self):
+        # In case of thread ID:
+        # - pid_exists() is supposed to return False
+        # - Process(tid) is supposed to work
+        # - pids() should not return the TID
+        # See: https://github.com/giampaolo/psutil/issues/687
+        with ThreadTask():
+            p = psutil.Process()
+            threads = p.threads()
+            assert len(threads) == (3 if QEMU_USER else 2)
+            tid = sorted(threads, key=lambda x: x.id)[1].id
+            assert p.pid != tid
+            pt = psutil.Process(tid)
+            pt.as_dict()
+            assert tid not in psutil.pids()
+
+    def test_pid_exists_no_proc_status(self):
+        # Internally pid_exists relies on /proc/{pid}/status.
+        # Emulate a case where this file is empty in which case
+        # psutil is supposed to fall back on using pids().
+        with mock_open_content({"/proc/%s/status": ""}) as m:
+            assert psutil.pid_exists(os.getpid())
+            assert m.called
+
+
+# =====================================================================
+# --- sensors
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+@pytest.mark.skipif(not HAS_BATTERY, reason="no battery")
+class TestSensorsBattery(PsutilTestCase):
+    @pytest.mark.skipif(not which("acpi"), reason="acpi utility not available")
+    def test_percent(self):
+        out = sh("acpi -b")
+        acpi_value = int(out.split(",")[1].strip().replace('%', ''))
+        psutil_value = psutil.sensors_battery().percent
+        assert abs(acpi_value - psutil_value) < 1
+
+    def test_emulate_power_plugged(self):
+        # Pretend the AC power cable is connected.
+        def open_mock(name, *args, **kwargs):
+            if name.endswith(('AC0/online', 'AC/online')):
+                return io.BytesIO(b"1")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock) as m:
+            assert psutil.sensors_battery().power_plugged is True
+            assert (
+                psutil.sensors_battery().secsleft
+                == psutil.POWER_TIME_UNLIMITED
+            )
+            assert m.called
+
+    def test_emulate_power_plugged_2(self):
+        # Same as above but pretend /AC0/online does not exist in which
+        # case code relies on /status file.
+        def open_mock(name, *args, **kwargs):
+            if name.endswith(('AC0/online', 'AC/online')):
+                raise IOError(errno.ENOENT, "")
+            elif name.endswith("/status"):
+                return io.StringIO(u"charging")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock) as m:
+            assert psutil.sensors_battery().power_plugged is True
+            assert m.called
+
+    def test_emulate_power_not_plugged(self):
+        # Pretend the AC power cable is not connected.
+        def open_mock(name, *args, **kwargs):
+            if name.endswith(('AC0/online', 'AC/online')):
+                return io.BytesIO(b"0")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock) as m:
+            assert psutil.sensors_battery().power_plugged is False
+            assert m.called
+
+    def test_emulate_power_not_plugged_2(self):
+        # Same as above but pretend /AC0/online does not exist in which
+        # case code relies on /status file.
+        def open_mock(name, *args, **kwargs):
+            if name.endswith(('AC0/online', 'AC/online')):
+                raise IOError(errno.ENOENT, "")
+            elif name.endswith("/status"):
+                return io.StringIO(u"discharging")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock) as m:
+            assert psutil.sensors_battery().power_plugged is False
+            assert m.called
+
+    def test_emulate_power_undetermined(self):
+        # Pretend we can't know whether the AC power cable not
+        # connected (assert fallback to False).
+        def open_mock(name, *args, **kwargs):
+            if name.startswith((
+                '/sys/class/power_supply/AC0/online',
+                '/sys/class/power_supply/AC/online',
+            )):
+                raise IOError(errno.ENOENT, "")
+            elif name.startswith("/sys/class/power_supply/BAT0/status"):
+                return io.BytesIO(b"???")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock) as m:
+            assert psutil.sensors_battery().power_plugged is None
+            assert m.called
+
+    def test_emulate_energy_full_0(self):
+        # Emulate a case where energy_full files returns 0.
+        with mock_open_content(
+            {"/sys/class/power_supply/BAT0/energy_full": b"0"}
+        ) as m:
+            assert psutil.sensors_battery().percent == 0
+            assert m.called
+
+    def test_emulate_energy_full_not_avail(self):
+        # Emulate a case where energy_full file does not exist.
+        # Expected fallback on /capacity.
+        with mock_open_exception(
+            "/sys/class/power_supply/BAT0/energy_full",
+            IOError(errno.ENOENT, ""),
+        ):
+            with mock_open_exception(
+                "/sys/class/power_supply/BAT0/charge_full",
+                IOError(errno.ENOENT, ""),
+            ):
+                with mock_open_content(
+                    {"/sys/class/power_supply/BAT0/capacity": b"88"}
+                ):
+                    assert psutil.sensors_battery().percent == 88
+
+    def test_emulate_no_power(self):
+        # Emulate a case where /AC0/online file nor /BAT0/status exist.
+        with mock_open_exception(
+            "/sys/class/power_supply/AC/online", IOError(errno.ENOENT, "")
+        ):
+            with mock_open_exception(
+                "/sys/class/power_supply/AC0/online", IOError(errno.ENOENT, "")
+            ):
+                with mock_open_exception(
+                    "/sys/class/power_supply/BAT0/status",
+                    IOError(errno.ENOENT, ""),
+                ):
+                    assert psutil.sensors_battery().power_plugged is None
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSensorsBatteryEmulated(PsutilTestCase):
+    def test_it(self):
+        def open_mock(name, *args, **kwargs):
+            if name.endswith("/energy_now"):
+                return io.StringIO(u"60000000")
+            elif name.endswith("/power_now"):
+                return io.StringIO(u"0")
+            elif name.endswith("/energy_full"):
+                return io.StringIO(u"60000001")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch('os.listdir', return_value=["BAT0"]) as mlistdir:
+            with mock.patch(patch_point, side_effect=open_mock) as mopen:
+                assert psutil.sensors_battery() is not None
+        assert mlistdir.called
+        assert mopen.called
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSensorsTemperatures(PsutilTestCase):
+    def test_emulate_class_hwmon(self):
+        def open_mock(name, *args, **kwargs):
+            if name.endswith('/name'):
+                return io.StringIO(u"name")
+            elif name.endswith('/temp1_label'):
+                return io.StringIO(u"label")
+            elif name.endswith('/temp1_input'):
+                return io.BytesIO(b"30000")
+            elif name.endswith('/temp1_max'):
+                return io.BytesIO(b"40000")
+            elif name.endswith('/temp1_crit'):
+                return io.BytesIO(b"50000")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            # Test case with /sys/class/hwmon
+            with mock.patch(
+                'glob.glob', return_value=['/sys/class/hwmon/hwmon0/temp1']
+            ):
+                temp = psutil.sensors_temperatures()['name'][0]
+                assert temp.label == 'label'
+                assert temp.current == 30.0
+                assert temp.high == 40.0
+                assert temp.critical == 50.0
+
+    def test_emulate_class_thermal(self):
+        def open_mock(name, *args, **kwargs):
+            if name.endswith('0_temp'):
+                return io.BytesIO(b"50000")
+            elif name.endswith('temp'):
+                return io.BytesIO(b"30000")
+            elif name.endswith('0_type'):
+                return io.StringIO(u"critical")
+            elif name.endswith('type'):
+                return io.StringIO(u"name")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        def glob_mock(path):
+            if path == '/sys/class/hwmon/hwmon*/temp*_*':  # noqa
+                return []
+            elif path == '/sys/class/hwmon/hwmon*/device/temp*_*':
+                return []
+            elif path == '/sys/class/thermal/thermal_zone*':
+                return ['/sys/class/thermal/thermal_zone0']
+            elif path == '/sys/class/thermal/thermal_zone0/trip_point*':
+                return [
+                    '/sys/class/thermal/thermal_zone1/trip_point_0_type',
+                    '/sys/class/thermal/thermal_zone1/trip_point_0_temp',
+                ]
+            return []
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            with mock.patch('glob.glob', create=True, side_effect=glob_mock):
+                temp = psutil.sensors_temperatures()['name'][0]
+                assert temp.label == ''  # noqa
+                assert temp.current == 30.0
+                assert temp.high == 50.0
+                assert temp.critical == 50.0
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestSensorsFans(PsutilTestCase):
+    def test_emulate_data(self):
+        def open_mock(name, *args, **kwargs):
+            if name.endswith('/name'):
+                return io.StringIO(u"name")
+            elif name.endswith('/fan1_label'):
+                return io.StringIO(u"label")
+            elif name.endswith('/fan1_input'):
+                return io.StringIO(u"2000")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock):
+            with mock.patch(
+                'glob.glob', return_value=['/sys/class/hwmon/hwmon2/fan1']
+            ):
+                fan = psutil.sensors_fans()['name'][0]
+                assert fan.label == 'label'
+                assert fan.current == 2000
+
+
+# =====================================================================
+# --- test process
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestProcess(PsutilTestCase):
+    @retry_on_failure()
+    def test_parse_smaps_vs_memory_maps(self):
+        sproc = self.spawn_testproc()
+        uss, pss, swap = psutil._pslinux.Process(sproc.pid)._parse_smaps()
+        maps = psutil.Process(sproc.pid).memory_maps(grouped=False)
+        assert (
+            abs(uss - sum([x.private_dirty + x.private_clean for x in maps]))
+            < 4096
+        )
+        assert abs(pss - sum([x.pss for x in maps])) < 4096
+        assert abs(swap - sum([x.swap for x in maps])) < 4096
+
+    def test_parse_smaps_mocked(self):
+        # See: https://github.com/giampaolo/psutil/issues/1222
+        content = textwrap.dedent("""\
+            fffff0 r-xp 00000000 00:00 0                  [vsyscall]
+            Size:                  1 kB
+            Rss:                   2 kB
+            Pss:                   3 kB
+            Shared_Clean:          4 kB
+            Shared_Dirty:          5 kB
+            Private_Clean:         6 kB
+            Private_Dirty:         7 kB
+            Referenced:            8 kB
+            Anonymous:             9 kB
+            LazyFree:              10 kB
+            AnonHugePages:         11 kB
+            ShmemPmdMapped:        12 kB
+            Shared_Hugetlb:        13 kB
+            Private_Hugetlb:       14 kB
+            Swap:                  15 kB
+            SwapPss:               16 kB
+            KernelPageSize:        17 kB
+            MMUPageSize:           18 kB
+            Locked:                19 kB
+            VmFlags: rd ex
+            """).encode()
+        with mock_open_content({"/proc/%s/smaps" % os.getpid(): content}) as m:
+            p = psutil._pslinux.Process(os.getpid())
+            uss, pss, swap = p._parse_smaps()
+            assert m.called
+            assert uss == (6 + 7 + 14) * 1024
+            assert pss == 3 * 1024
+            assert swap == 15 * 1024
+
+    # On PYPY file descriptors are not closed fast enough.
+    @pytest.mark.skipif(PYPY, reason="unreliable on PYPY")
+    def test_open_files_mode(self):
+        def get_test_file(fname):
+            p = psutil.Process()
+            giveup_at = time.time() + GLOBAL_TIMEOUT
+            while True:
+                for file in p.open_files():
+                    if file.path == os.path.abspath(fname):
+                        return file
+                    elif time.time() > giveup_at:
+                        break
+            raise RuntimeError("timeout looking for test file")
+
+        testfn = self.get_testfn()
+        with open(testfn, "w"):
+            assert get_test_file(testfn).mode == "w"
+        with open(testfn):
+            assert get_test_file(testfn).mode == "r"
+        with open(testfn, "a"):
+            assert get_test_file(testfn).mode == "a"
+        with open(testfn, "r+"):
+            assert get_test_file(testfn).mode == "r+"
+        with open(testfn, "w+"):
+            assert get_test_file(testfn).mode == "r+"
+        with open(testfn, "a+"):
+            assert get_test_file(testfn).mode == "a+"
+        # note: "x" bit is not supported
+        if PY3:
+            safe_rmpath(testfn)
+            with open(testfn, "x"):
+                assert get_test_file(testfn).mode == "w"
+            safe_rmpath(testfn)
+            with open(testfn, "x+"):
+                assert get_test_file(testfn).mode == "r+"
+
+    def test_open_files_file_gone(self):
+        # simulates a file which gets deleted during open_files()
+        # execution
+        p = psutil.Process()
+        files = p.open_files()
+        with open(self.get_testfn(), 'w'):
+            # give the kernel some time to see the new file
+            call_until(lambda: len(p.open_files()) != len(files))
+            with mock.patch(
+                'psutil._pslinux.os.readlink',
+                side_effect=OSError(errno.ENOENT, ""),
+            ) as m:
+                assert p.open_files() == []
+                assert m.called
+            # also simulate the case where os.readlink() returns EINVAL
+            # in which case psutil is supposed to 'continue'
+            with mock.patch(
+                'psutil._pslinux.os.readlink',
+                side_effect=OSError(errno.EINVAL, ""),
+            ) as m:
+                assert p.open_files() == []
+                assert m.called
+
+    def test_open_files_fd_gone(self):
+        # Simulate a case where /proc/{pid}/fdinfo/{fd} disappears
+        # while iterating through fds.
+        # https://travis-ci.org/giampaolo/psutil/jobs/225694530
+        p = psutil.Process()
+        files = p.open_files()
+        with open(self.get_testfn(), 'w'):
+            # give the kernel some time to see the new file
+            call_until(lambda: len(p.open_files()) != len(files))
+            patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+            with mock.patch(
+                patch_point, side_effect=IOError(errno.ENOENT, "")
+            ) as m:
+                assert p.open_files() == []
+                assert m.called
+
+    def test_open_files_enametoolong(self):
+        # Simulate a case where /proc/{pid}/fd/{fd} symlink
+        # points to a file with full path longer than PATH_MAX, see:
+        # https://github.com/giampaolo/psutil/issues/1940
+        p = psutil.Process()
+        files = p.open_files()
+        with open(self.get_testfn(), 'w'):
+            # give the kernel some time to see the new file
+            call_until(lambda: len(p.open_files()) != len(files))
+            patch_point = 'psutil._pslinux.os.readlink'
+            with mock.patch(
+                patch_point, side_effect=OSError(errno.ENAMETOOLONG, "")
+            ) as m:
+                with mock.patch("psutil._pslinux.debug"):
+                    assert p.open_files() == []
+                    assert m.called
+
+    # --- mocked tests
+
+    def test_terminal_mocked(self):
+        with mock.patch(
+            'psutil._pslinux._psposix.get_terminal_map', return_value={}
+        ) as m:
+            assert psutil._pslinux.Process(os.getpid()).terminal() is None
+            assert m.called
+
+    # TODO: re-enable this test.
+    # def test_num_ctx_switches_mocked(self):
+    #     with mock.patch('psutil._common.open', create=True) as m:
+    #         self.assertRaises(
+    #             NotImplementedError,
+    #             psutil._pslinux.Process(os.getpid()).num_ctx_switches)
+    #         assert m.called
+
+    def test_cmdline_mocked(self):
+        # see: https://github.com/giampaolo/psutil/issues/639
+        p = psutil.Process()
+        fake_file = io.StringIO(u'foo\x00bar\x00')
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m:
+            assert p.cmdline() == ['foo', 'bar']
+            assert m.called
+        fake_file = io.StringIO(u'foo\x00bar\x00\x00')
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m:
+            assert p.cmdline() == ['foo', 'bar', '']
+            assert m.called
+
+    def test_cmdline_spaces_mocked(self):
+        # see: https://github.com/giampaolo/psutil/issues/1179
+        p = psutil.Process()
+        fake_file = io.StringIO(u'foo bar ')
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m:
+            assert p.cmdline() == ['foo', 'bar']
+            assert m.called
+        fake_file = io.StringIO(u'foo bar  ')
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m:
+            assert p.cmdline() == ['foo', 'bar', '']
+            assert m.called
+
+    def test_cmdline_mixed_separators(self):
+        # https://github.com/giampaolo/psutil/issues/
+        #    1179#issuecomment-552984549
+        p = psutil.Process()
+        fake_file = io.StringIO(u'foo\x20bar\x00')
+        with mock.patch(
+            'psutil._common.open', return_value=fake_file, create=True
+        ) as m:
+            assert p.cmdline() == ['foo', 'bar']
+            assert m.called
+
+    def test_readlink_path_deleted_mocked(self):
+        with mock.patch(
+            'psutil._pslinux.os.readlink', return_value='/home/foo (deleted)'
+        ):
+            assert psutil.Process().exe() == "/home/foo"
+            assert psutil.Process().cwd() == "/home/foo"
+
+    def test_threads_mocked(self):
+        # Test the case where os.listdir() returns a file (thread)
+        # which no longer exists by the time we open() it (race
+        # condition). threads() is supposed to ignore that instead
+        # of raising NSP.
+        def open_mock_1(name, *args, **kwargs):
+            if name.startswith('/proc/%s/task' % os.getpid()):
+                raise IOError(errno.ENOENT, "")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        orig_open = open
+        patch_point = 'builtins.open' if PY3 else '__builtin__.open'
+        with mock.patch(patch_point, side_effect=open_mock_1) as m:
+            ret = psutil.Process().threads()
+            assert m.called
+            assert ret == []
+
+        # ...but if it bumps into something != ENOENT we want an
+        # exception.
+        def open_mock_2(name, *args, **kwargs):
+            if name.startswith('/proc/%s/task' % os.getpid()):
+                raise IOError(errno.EPERM, "")
+            else:
+                return orig_open(name, *args, **kwargs)
+
+        with mock.patch(patch_point, side_effect=open_mock_2):
+            with pytest.raises(psutil.AccessDenied):
+                psutil.Process().threads()
+
+    def test_exe_mocked(self):
+        with mock.patch(
+            'psutil._pslinux.readlink', side_effect=OSError(errno.ENOENT, "")
+        ) as m:
+            # de-activate guessing from cmdline()
+            with mock.patch(
+                'psutil._pslinux.Process.cmdline', return_value=[]
+            ):
+                ret = psutil.Process().exe()
+                assert m.called
+                assert ret == ""  # noqa
+
+    def test_issue_1014(self):
+        # Emulates a case where smaps file does not exist. In this case
+        # wrap_exception decorator should not raise NoSuchProcess.
+        with mock_open_exception(
+            '/proc/%s/smaps' % os.getpid(), IOError(errno.ENOENT, "")
+        ) as m:
+            p = psutil.Process()
+            with pytest.raises(FileNotFoundError):
+                p.memory_maps()
+            assert m.called
+
+    def test_issue_2418(self):
+        p = psutil.Process()
+        with mock_open_exception(
+            '/proc/%s/statm' % os.getpid(), FileNotFoundError
+        ):
+            with mock.patch("os.path.exists", return_value=False):
+                with pytest.raises(psutil.NoSuchProcess):
+                    p.memory_info()
+
+    @pytest.mark.skipif(not HAS_RLIMIT, reason="not supported")
+    def test_rlimit_zombie(self):
+        # Emulate a case where rlimit() raises ENOSYS, which may
+        # happen in case of zombie process:
+        # https://travis-ci.org/giampaolo/psutil/jobs/51368273
+        with mock.patch(
+            "psutil._pslinux.prlimit", side_effect=OSError(errno.ENOSYS, "")
+        ) as m1:
+            with mock.patch(
+                "psutil._pslinux.Process._is_zombie", return_value=True
+            ) as m2:
+                p = psutil.Process()
+                p.name()
+                with pytest.raises(psutil.ZombieProcess) as cm:
+                    p.rlimit(psutil.RLIMIT_NOFILE)
+        assert m1.called
+        assert m2.called
+        assert cm.value.pid == p.pid
+        assert cm.value.name == p.name()
+
+    def test_stat_file_parsing(self):
+        args = [
+            "0",  # pid
+            "(cat)",  # name
+            "Z",  # status
+            "1",  # ppid
+            "0",  # pgrp
+            "0",  # session
+            "0",  # tty
+            "0",  # tpgid
+            "0",  # flags
+            "0",  # minflt
+            "0",  # cminflt
+            "0",  # majflt
+            "0",  # cmajflt
+            "2",  # utime
+            "3",  # stime
+            "4",  # cutime
+            "5",  # cstime
+            "0",  # priority
+            "0",  # nice
+            "0",  # num_threads
+            "0",  # itrealvalue
+            "6",  # starttime
+            "0",  # vsize
+            "0",  # rss
+            "0",  # rsslim
+            "0",  # startcode
+            "0",  # endcode
+            "0",  # startstack
+            "0",  # kstkesp
+            "0",  # kstkeip
+            "0",  # signal
+            "0",  # blocked
+            "0",  # sigignore
+            "0",  # sigcatch
+            "0",  # wchan
+            "0",  # nswap
+            "0",  # cnswap
+            "0",  # exit_signal
+            "6",  # processor
+            "0",  # rt priority
+            "0",  # policy
+            "7",  # delayacct_blkio_ticks
+        ]
+        content = " ".join(args).encode()
+        with mock_open_content({"/proc/%s/stat" % os.getpid(): content}):
+            p = psutil.Process()
+            assert p.name() == 'cat'
+            assert p.status() == psutil.STATUS_ZOMBIE
+            assert p.ppid() == 1
+            assert p.create_time() == 6 / CLOCK_TICKS + psutil.boot_time()
+            cpu = p.cpu_times()
+            assert cpu.user == 2 / CLOCK_TICKS
+            assert cpu.system == 3 / CLOCK_TICKS
+            assert cpu.children_user == 4 / CLOCK_TICKS
+            assert cpu.children_system == 5 / CLOCK_TICKS
+            assert cpu.iowait == 7 / CLOCK_TICKS
+            assert p.cpu_num() == 6
+
+    def test_status_file_parsing(self):
+        content = textwrap.dedent("""\
+            Uid:\t1000\t1001\t1002\t1003
+            Gid:\t1004\t1005\t1006\t1007
+            Threads:\t66
+            Cpus_allowed:\tf
+            Cpus_allowed_list:\t0-7
+            voluntary_ctxt_switches:\t12
+            nonvoluntary_ctxt_switches:\t13""").encode()
+        with mock_open_content({"/proc/%s/status" % os.getpid(): content}):
+            p = psutil.Process()
+            assert p.num_ctx_switches().voluntary == 12
+            assert p.num_ctx_switches().involuntary == 13
+            assert p.num_threads() == 66
+            uids = p.uids()
+            assert uids.real == 1000
+            assert uids.effective == 1001
+            assert uids.saved == 1002
+            gids = p.gids()
+            assert gids.real == 1004
+            assert gids.effective == 1005
+            assert gids.saved == 1006
+            assert p._proc._get_eligible_cpus() == list(range(8))
+
+    def test_net_connections_enametoolong(self):
+        # Simulate a case where /proc/{pid}/fd/{fd} symlink points to
+        # a file with full path longer than PATH_MAX, see:
+        # https://github.com/giampaolo/psutil/issues/1940
+        with mock.patch(
+            'psutil._pslinux.os.readlink',
+            side_effect=OSError(errno.ENAMETOOLONG, ""),
+        ) as m:
+            p = psutil.Process()
+            with mock.patch("psutil._pslinux.debug"):
+                assert p.net_connections() == []
+                assert m.called
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestProcessAgainstStatus(PsutilTestCase):
+    """/proc/pid/stat and /proc/pid/status have many values in common.
+    Whenever possible, psutil uses /proc/pid/stat (it's faster).
+    For all those cases we check that the value found in
+    /proc/pid/stat (by psutil) matches the one found in
+    /proc/pid/status.
+    """
+
+    @classmethod
+    def setUpClass(cls):
+        cls.proc = psutil.Process()
+
+    def read_status_file(self, linestart):
+        with psutil._psplatform.open_text(
+            '/proc/%s/status' % self.proc.pid
+        ) as f:
+            for line in f:
+                line = line.strip()
+                if line.startswith(linestart):
+                    value = line.partition('\t')[2]
+                    try:
+                        return int(value)
+                    except ValueError:
+                        return value
+            raise ValueError("can't find %r" % linestart)
+
+    def test_name(self):
+        value = self.read_status_file("Name:")
+        assert self.proc.name() == value
+
+    @pytest.mark.skipif(QEMU_USER, reason="QEMU user not supported")
+    def test_status(self):
+        value = self.read_status_file("State:")
+        value = value[value.find('(') + 1 : value.rfind(')')]
+        value = value.replace(' ', '-')
+        assert self.proc.status() == value
+
+    def test_ppid(self):
+        value = self.read_status_file("PPid:")
+        assert self.proc.ppid() == value
+
+    def test_num_threads(self):
+        value = self.read_status_file("Threads:")
+        assert self.proc.num_threads() == value
+
+    def test_uids(self):
+        value = self.read_status_file("Uid:")
+        value = tuple(map(int, value.split()[1:4]))
+        assert self.proc.uids() == value
+
+    def test_gids(self):
+        value = self.read_status_file("Gid:")
+        value = tuple(map(int, value.split()[1:4]))
+        assert self.proc.gids() == value
+
+    @retry_on_failure()
+    def test_num_ctx_switches(self):
+        value = self.read_status_file("voluntary_ctxt_switches:")
+        assert self.proc.num_ctx_switches().voluntary == value
+        value = self.read_status_file("nonvoluntary_ctxt_switches:")
+        assert self.proc.num_ctx_switches().involuntary == value
+
+    def test_cpu_affinity(self):
+        value = self.read_status_file("Cpus_allowed_list:")
+        if '-' in str(value):
+            min_, max_ = map(int, value.split('-'))
+            assert self.proc.cpu_affinity() == list(range(min_, max_ + 1))
+
+    def test_cpu_affinity_eligible_cpus(self):
+        value = self.read_status_file("Cpus_allowed_list:")
+        with mock.patch("psutil._pslinux.per_cpu_times") as m:
+            self.proc._proc._get_eligible_cpus()
+        if '-' in str(value):
+            assert not m.called
+        else:
+            assert m.called
+
+
+# =====================================================================
+# --- test utils
+# =====================================================================
+
+
+@pytest.mark.skipif(not LINUX, reason="LINUX only")
+class TestUtils(PsutilTestCase):
+    def test_readlink(self):
+        with mock.patch("os.readlink", return_value="foo (deleted)") as m:
+            assert psutil._psplatform.readlink("bar") == "foo"
+            assert m.called