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authorS. Solomon Darnell2025-03-28 21:52:21 -0500
committerS. Solomon Darnell2025-03-28 21:52:21 -0500
commit4a52a71956a8d46fcb7294ac71734504bb09bcc2 (patch)
treeee3dc5af3b6313e921cd920906356f5d4febc4ed /.venv/lib/python3.12/site-packages/bs4/tests/test_tree.py
parentcc961e04ba734dd72309fb548a2f97d67d578813 (diff)
downloadgn-ai-master.tar.gz
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+# -*- coding: utf-8 -*-
+"""Tests for Beautiful Soup's tree traversal methods.
+
+The tree traversal methods are the main advantage of using Beautiful
+Soup over just using a parser.
+
+Different parsers will build different Beautiful Soup trees given the
+same markup, but all Beautiful Soup trees can be traversed with the
+methods tested here.
+"""
+
+import pytest
+import re
+import warnings
+from bs4 import BeautifulSoup
+from bs4.builder import builder_registry
+from bs4.element import (
+    AttributeResemblesVariableWarning,
+    CData,
+    Comment,
+    NavigableString,
+    Tag,
+)
+from bs4.filter import SoupStrainer
+from . import (
+    SoupTest,
+)
+
+
+class TestFind(SoupTest):
+    """Basic tests of the find() method.
+    """
+
+    def test_find_tag(self):
+        soup = self.soup("<a>1</a><b>2</b><a>3</a><b>4</b>")
+        assert soup.find("b").string == "2"
+
+    def test_unicode_text_find(self):
+        soup = self.soup("<h1>Räksmörgås</h1>")
+        assert soup.find(string="Räksmörgås") == "Räksmörgås"
+
+    def test_unicode_attribute_find(self):
+        soup = self.soup('<h1 id="Räksmörgås">here it is</h1>')
+        str(soup)
+        assert "here it is" == soup.find(id="Räksmörgås").text
+
+    def test_find_everything(self):
+        """Test an optimization that finds all tags."""
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        assert 2 == len(soup.find_all())
+
+    def test_find_everything_with_name(self):
+        """Test an optimization that finds all tags with a given name."""
+        soup = self.soup("<a>foo</a><b>bar</b><a>baz</a>")
+        assert 2 == len(soup.find_all("a"))
+
+    def test_find_with_no_arguments(self):
+        soup = self.soup("<div></div><p></p>")
+        assert "div" == soup.find().name
+        assert "div" == soup.find("p").find_previous_sibling().name
+        assert "p" == soup.find("div").find_next_sibling().name
+
+    def test_find_with_no_arguments_only_finds_tags(self):
+        soup = self.soup("text<div>text</div>text<p>text</p>")
+        assert "div" == soup.find().name
+        assert "div" == soup.find("p").find_previous_sibling().name
+        assert "p" == soup.find("div").find_next_sibling().name
+
+
+class TestFindAll(SoupTest):
+    """Basic tests of the find_all() method."""
+
+    def test_find_all_with_no_arguments_only_finds_tags(self):
+        soup = self.soup("<body>text<div>text</div>text<p>text</p></body>")
+        assert 2 == len(soup.body.find_all())
+        assert 1 == len(soup.find("p").find_previous_siblings())
+        assert 1 == len(soup.find("div").find_next_siblings())
+
+    def test_find_all_text_nodes(self):
+        """You can search the tree for text nodes."""
+        soup = self.soup("<html>Foo<b>bar</b>\xbb</html>")
+        # Exact match.
+        assert soup.find_all(string="bar") == ["bar"]
+
+        # Match any of a number of strings.
+        assert soup.find_all(string=["Foo", "bar"]) == ["Foo", "bar"]
+        # Match a regular expression.
+        assert soup.find_all(string=re.compile(".*")) == ["Foo", "bar", "\xbb"]
+        # Match anything.
+        assert soup.find_all(string=True) == ["Foo", "bar", "\xbb"]
+
+    def test_find_all_limit(self):
+        """You can limit the number of items returned by find_all."""
+        soup = self.soup("<a>1</a><a>2</a><a>3</a><a>4</a><a>5</a>")
+        self.assert_selects(soup.find_all("a", limit=3), ["1", "2", "3"])
+        self.assert_selects(soup.find_all("a", limit=1), ["1"])
+        self.assert_selects(soup.find_all("a", limit=10), ["1", "2", "3", "4", "5"])
+
+        # A limit of 0 means no limit.
+        self.assert_selects(soup.find_all("a", limit=0), ["1", "2", "3", "4", "5"])
+
+    def test_calling_a_tag_is_calling_findall(self):
+        soup = self.soup("<a>1</a><b>2<a id='foo'>3</a></b>")
+        self.assert_selects(soup("a", limit=1), ["1"])
+        self.assert_selects(soup.b(id="foo"), ["3"])
+
+    def test_find_all_with_self_referential_data_structure_does_not_cause_infinite_recursion(
+        self,
+    ):
+        soup = self.soup("<a></a>")
+        # Create a self-referential list.
+        selfref = []
+        selfref.append(selfref)
+
+        # Without special code in SoupStrainer, this would cause infinite
+        # recursion.
+        with warnings.catch_warnings(record=True) as w:
+            assert [] == soup.find_all(selfref)
+            [warning] = w
+            assert warning.filename == __file__
+            msg = str(warning.message)
+            assert (
+                msg
+                == "Ignoring nested list [[...]] to avoid the possibility of infinite recursion."
+            )
+
+    def test_find_all_resultset(self):
+        """All find_all calls return a ResultSet"""
+        soup = self.soup("<a></a>")
+        result = soup.find_all("a")
+        assert hasattr(result, "source")
+
+        result = soup.find_all(True)
+        assert hasattr(result, "source")
+
+        result = soup.find_all(string="foo")
+        assert hasattr(result, "source")
+
+
+class TestFindAllBasicNamespaces(SoupTest):
+    def test_find_by_namespaced_name(self):
+        soup = self.soup('<mathml:msqrt>4</mathml:msqrt><a svg:fill="red">')
+        assert "4" == soup.find("mathml:msqrt").string
+        assert "a" == soup.find(attrs={"svg:fill": "red"}).name
+
+
+class TestFindAllByName(SoupTest):
+    """Test ways of finding tags by tag name."""
+
+    def setup_method(self) -> None:
+        self.tree = self.soup("""<a>First tag.</a>
+                                  <b>Second tag.</b>
+                                  <c>Third <a>Nested tag.</a> tag.</c>""")
+
+    def test_find_all_by_tag_name(self):
+        # Find all the <a> tags.
+        self.assert_selects(self.tree.find_all("a"), ["First tag.", "Nested tag."])
+
+    def test_find_all_by_name_and_text(self):
+        self.assert_selects(
+            self.tree.find_all("a", string="First tag."), ["First tag."]
+        )
+
+        self.assert_selects(
+            self.tree.find_all("a", string=True), ["First tag.", "Nested tag."]
+        )
+
+        self.assert_selects(
+            self.tree.find_all("a", string=re.compile("tag")),
+            ["First tag.", "Nested tag."],
+        )
+
+    def test_find_all_on_non_root_element(self):
+        # You can call find_all on any node, not just the root.
+        self.assert_selects(self.tree.c.find_all("a"), ["Nested tag."])
+
+    def test_calling_element_invokes_find_all(self):
+        self.assert_selects(self.tree("a"), ["First tag.", "Nested tag."])
+
+    def test_find_all_by_tag_strainer(self):
+        self.assert_selects(
+            self.tree.find_all(SoupStrainer("a")), ["First tag.", "Nested tag."]
+        )
+
+    def test_find_all_by_tag_names(self):
+        self.assert_selects(
+            self.tree.find_all(["a", "b"]), ["First tag.", "Second tag.", "Nested tag."]
+        )
+
+    def test_find_all_by_tag_dict(self):
+        self.assert_selects(
+            self.tree.find_all({"a": True, "b": True}),
+            ["First tag.", "Second tag.", "Nested tag."],
+        )
+
+    def test_find_all_by_tag_re(self):
+        self.assert_selects(
+            self.tree.find_all(re.compile("^[ab]$")),
+            ["First tag.", "Second tag.", "Nested tag."],
+        )
+
+    def test_find_all_with_tags_matching_method(self):
+        # You can define an oracle method that determines whether
+        # a tag matches the search.
+        def id_matches_name(tag):
+            return tag.name == tag.get("id")
+
+        tree = self.soup("""<a id="a">Match 1.</a>
+                            <a id="1">Does not match.</a>
+                            <b id="b">Match 2.</a>""")
+
+        self.assert_selects(tree.find_all(id_matches_name), ["Match 1.", "Match 2."])
+
+    def test_find_with_multi_valued_attribute(self):
+        soup = self.soup(
+            "<div class='a b'>1</div><div class='a c'>2</div><div class='a d'>3</div>"
+        )
+        r1 = soup.find("div", "a d")
+        r2 = soup.find("div", re.compile(r"a d"))
+        r3, r4 = soup.find_all("div", ["a b", "a d"])
+        assert "3" == r1.string
+        assert "3" == r2.string
+        assert "1" == r3.string
+        assert "3" == r4.string
+
+
+class TestFindAllByAttribute(SoupTest):
+    def test_find_all_by_attribute_name(self):
+        # You can pass in keyword arguments to find_all to search by
+        # attribute.
+        tree = self.soup("""
+                         <a id="first">Matching a.</a>
+                         <a id="second">
+                          Non-matching <b id="first">Matching b.</b>a.
+                         </a>""")
+        self.assert_selects(tree.find_all(id="first"), ["Matching a.", "Matching b."])
+
+    def test_find_all_by_utf8_attribute_value(self):
+        peace = "םולש".encode("utf8")
+        data = '<a title="םולש"></a>'.encode("utf8")
+        soup = self.soup(data)
+        assert [soup.a] == soup.find_all(title=peace)
+        assert [soup.a] == soup.find_all(title=peace.decode("utf8"))
+        assert [soup.a], soup.find_all(title=[peace, "something else"])
+
+    def test_find_all_by_attribute_dict(self):
+        # You can pass in a dictionary as the argument 'attrs'. This
+        # lets you search for attributes like 'name' (a fixed argument
+        # to find_all) and 'class' (a reserved word in Python.)
+        tree = self.soup("""
+                         <a name="name1" class="class1">Name match.</a>
+                         <a name="name2" class="class2">Class match.</a>
+                         <a name="name3" class="class3">Non-match.</a>
+                         <name1>A tag called 'name1'.</name1>
+                         """)
+
+        # This doesn't do what you want.
+        self.assert_selects(tree.find_all(name="name1"), ["A tag called 'name1'."])
+        # This does what you want.
+        self.assert_selects(tree.find_all(attrs={"name": "name1"}), ["Name match."])
+
+        self.assert_selects(tree.find_all(attrs={"class": "class2"}), ["Class match."])
+
+    def test_find_all_by_class(self):
+        tree = self.soup("""
+                         <a class="1">Class 1.</a>
+                         <a class="2">Class 2.</a>
+                         <b class="1">Class 1.</b>
+                         <c class="3 4">Class 3 and 4.</c>
+                         """)
+
+        # Passing in the class_ keyword argument will search against
+        # the 'class' attribute.
+        self.assert_selects(tree.find_all("a", class_="1"), ["Class 1."])
+        self.assert_selects(tree.find_all("c", class_="3"), ["Class 3 and 4."])
+        self.assert_selects(tree.find_all("c", class_="4"), ["Class 3 and 4."])
+
+        # Passing in a string to 'attrs' will also search the CSS class.
+        self.assert_selects(tree.find_all("a", "1"), ["Class 1."])
+        self.assert_selects(tree.find_all(attrs="1"), ["Class 1.", "Class 1."])
+        self.assert_selects(tree.find_all("c", "3"), ["Class 3 and 4."])
+        self.assert_selects(tree.find_all("c", "4"), ["Class 3 and 4."])
+
+    def test_find_by_class_when_multiple_classes_present(self):
+        tree = self.soup("<gar class='foo bar'>Found it</gar>")
+
+        f = tree.find_all("gar", class_=re.compile("o"))
+        self.assert_selects(f, ["Found it"])
+
+        f = tree.find_all("gar", class_=re.compile("a"))
+        self.assert_selects(f, ["Found it"])
+
+        # If the search fails to match the individual strings "foo" and "bar",
+        # it will be tried against the combined string "foo bar".
+        f = tree.find_all("gar", class_=re.compile("o b"))
+        self.assert_selects(f, ["Found it"])
+
+    def test_find_all_with_non_dictionary_for_attrs_finds_by_class(self):
+        soup = self.soup("<a class='bar'>Found it</a>")
+
+        self.assert_selects(soup.find_all("a", re.compile("ba")), ["Found it"])
+
+        def big_attribute_value(value):
+            return len(value) > 3
+
+        self.assert_selects(soup.find_all("a", big_attribute_value), [])
+
+        def small_attribute_value(value):
+            return len(value) <= 3
+
+        self.assert_selects(soup.find_all("a", small_attribute_value), ["Found it"])
+
+    def test_find_all_with_string_for_attrs_finds_multiple_classes(self):
+        soup = self.soup('<a class="foo bar"></a><a class="foo"></a>')
+        a, a2 = soup.find_all("a")
+        assert [a, a2], soup.find_all("a", "foo")
+        assert [a], soup.find_all("a", "bar")
+
+        # If you specify the class as a string that contains a
+        # space, only that specific value will be found.
+        assert [a] == soup.find_all("a", class_="foo bar")
+        assert [a] == soup.find_all("a", "foo bar")
+        assert [] == soup.find_all("a", "bar foo")
+
+    def test_find_all_by_attribute_soupstrainer(self):
+        tree = self.soup("""
+                         <a id="first">Match.</a>
+                         <a id="second">Non-match.</a>""")
+
+        strainer = SoupStrainer(attrs={"id": "first"})
+        self.assert_selects(tree.find_all(strainer), ["Match."])
+
+    def test_find_all_with_missing_attribute(self):
+        # You can pass in None as the value of an attribute to find_all.
+        # This will match tags that do not have that attribute set.
+        tree = self.soup("""<a id="1">ID present.</a>
+                            <a>No ID present.</a>
+                            <a id="">ID is empty.</a>""")
+        self.assert_selects(tree.find_all("a", id=None), ["No ID present."])
+
+    def test_find_all_with_defined_attribute(self):
+        # You can pass in None as the value of an attribute to find_all.
+        # This will match tags that have that attribute set to any value.
+        tree = self.soup("""<a id="1">ID present.</a>
+                            <a>No ID present.</a>
+                            <a id="">ID is empty.</a>""")
+        self.assert_selects(tree.find_all(id=True), ["ID present.", "ID is empty."])
+
+    def test_find_all_with_numeric_attribute(self):
+        # If you search for a number, it's treated as a string.
+        tree = self.soup("""<a id=1>Unquoted attribute.</a>
+                            <a id="1">Quoted attribute.</a>""")
+
+        expected = ["Unquoted attribute.", "Quoted attribute."]
+        self.assert_selects(tree.find_all(id=1), expected)
+        self.assert_selects(tree.find_all(id="1"), expected)
+
+    def test_find_all_with_list_attribute_values(self):
+        # You can pass a list of attribute values instead of just one,
+        # and you'll get tags that match any of the values.
+        tree = self.soup("""<a id="1">1</a>
+                            <a id="2">2</a>
+                            <a id="3">3</a>
+                            <a>No ID.</a>""")
+        self.assert_selects(tree.find_all(id=["1", "3", "4"]), ["1", "3"])
+
+        # If you pass in an empty list, you get nothing.
+        self.assert_selects(tree.find_all(id=[]), [])
+
+    def test_find_all_with_regular_expression_attribute_value(self):
+        # You can pass a regular expression as an attribute value, and
+        # you'll get tags whose values for that attribute match the
+        # regular expression.
+        tree = self.soup("""<a id="a">One a.</a>
+                            <a id="aa">Two as.</a>
+                            <a id="ab">Mixed as and bs.</a>
+                            <a id="b">One b.</a>
+                            <a>No ID.</a>""")
+
+        self.assert_selects(tree.find_all(id=re.compile("^a+$")), ["One a.", "Two as."])
+
+    def test_find_by_name_and_containing_string(self):
+        soup = self.soup("<b>foo</b><b>bar</b><a>foo</a>")
+        a = soup.a
+
+        assert [a] == soup.find_all("a", string="foo")
+        assert [] == soup.find_all("a", string="bar")
+
+    def test_find_by_name_and_containing_string_when_string_is_buried(self):
+        soup = self.soup("<a>foo</a><a><b><c>foo</c></b></a>")
+        assert soup.find_all("a") == soup.find_all("a", string="foo")
+
+    def test_find_by_attribute_and_containing_string(self):
+        soup = self.soup('<b id="1">foo</b><a id="2">foo</a>')
+        a = soup.a
+
+        assert [a] == soup.find_all(id=2, string="foo")
+        assert [] == soup.find_all(id=1, string="bar")
+
+
+class TestSmooth(SoupTest):
+    """Test Tag.smooth."""
+
+    def test_smooth(self):
+        soup = self.soup("<div>a</div>")
+        div = soup.div
+        div.append("b")
+        div.append("c")
+        div.append(Comment("Comment 1"))
+        div.append(Comment("Comment 2"))
+        div.append("d")
+        builder = self.default_builder()
+        span = Tag(soup, builder, "span")
+        span.append("1")
+        span.append("2")
+        div.append(span)
+
+        # At this point the tree has a bunch of adjacent
+        # NavigableStrings. This is normal, but it has no meaning in
+        # terms of HTML, so we may want to smooth things out for
+        # output.
+
+        # Since the <span> tag has two children, its .string is None.
+        assert None is div.span.string
+
+        assert 7 == len(div.contents)
+        div.smooth()
+        assert 5 == len(div.contents)
+
+        # The three strings at the beginning of div.contents have been
+        # merged into on string.
+        #
+        assert "abc" == div.contents[0]
+
+        # The call is recursive -- the <span> tag was also smoothed.
+        assert "12" == div.span.string
+
+        # The two comments have _not_ been merged, even though
+        # comments are strings. Merging comments would change the
+        # meaning of the HTML.
+        assert "Comment 1" == div.contents[1]
+        assert "Comment 2" == div.contents[2]
+
+
+class TestIndex(SoupTest):
+    """Test Tag.index"""
+
+    def test_index(self):
+        tree = self.soup("""<div>
+                            <a>Identical</a>
+                            <b>Not identical</b>
+                            <a>Identical</a>
+
+                            <c><d>Identical with child</d></c>
+                            <b>Also not identical</b>
+                            <c><d>Identical with child</d></c>
+                            </div>""")
+        div = tree.div
+        for i, element in enumerate(div.contents):
+            assert i == div.index(element)
+        with pytest.raises(ValueError):
+            tree.index(1)
+
+
+class TestParentOperations(SoupTest):
+    """Test navigation and searching through an element's parents."""
+
+    def setup_method(self) -> None:
+        self.tree = self.soup("""<ul id="empty"></ul>
+                                 <ul id="top">
+                                  <ul id="middle">
+                                   <ul id="bottom">
+                                    <b id="start">Start here</b>
+                                   </ul>
+                                  </ul>""")
+        self.start = self.tree.b
+
+    def test_parent(self):
+        assert self.start.parent["id"] == "bottom"
+        assert self.start.parent.parent["id"] == "middle"
+        assert self.start.parent.parent.parent["id"] == "top"
+
+    def test_parent_of_top_tag_is_soup_object(self):
+        top_tag = self.tree.contents[0]
+        assert top_tag.parent == self.tree
+
+    def test_soup_object_has_no_parent(self):
+        assert None is self.tree.parent
+
+    def test_find_parents(self):
+        self.assert_selects_ids(
+            self.start.find_parents("ul"), ["bottom", "middle", "top"]
+        )
+        self.assert_selects_ids(self.start.find_parents("ul", id="middle"), ["middle"])
+        assert self.start.find_parents(id="start") == []
+
+    def test_find_parent(self):
+        # assert self.start.find_parent('ul')['id'] == 'bottom'
+        assert self.start.find_parent("ul", id="top")["id"] == "top"
+
+        assert self.start.find_parent(id="start") is None
+
+    def test_parent_of_text_element(self):
+        text = self.tree.find(string="Start here")
+        assert text.parent.name == "b"
+
+    def test_text_element_find_parent(self):
+        text = self.tree.find(string="Start here")
+        assert text.find_parent("ul")["id"] == "bottom"
+
+    def test_parent_generator(self):
+        parents = [
+            parent["id"]
+            for parent in self.start.parents
+            if parent is not None and "id" in parent.attrs
+        ]
+        assert parents == ["bottom", "middle", "top"]
+
+    def test_self_and_parent_generator(self):
+        results = [
+            parent["id"]
+            for parent in self.start.self_and_parents
+            if parent is not None and "id" in parent.attrs
+        ]
+        assert results == ["start", "bottom", "middle", "top"]
+
+
+class ProximityTest(SoupTest):
+    def setup_method(self) -> None:
+        self.tree = self.soup(
+            '<html id="start"><head id="headtag"></head><body id="bodytag"><b id="1">One</b><b id="2">Two</b><b id="3">Three</b></body></html>'
+        )
+
+
+class TestNextOperations(ProximityTest):
+    def setup_method(self) -> None:
+        super(TestNextOperations, self).setup_method()
+        self.start = self.tree.b
+
+    def test_next(self):
+        assert self.start.next_element == "One"
+        assert self.start.next_element.next_element["id"] == "2"
+
+    def test_next_of_last_item_is_none(self):
+        last = self.tree.find(string="Three")
+        assert last.next_element is None
+
+    def test_next_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        assert self.tree.next_element is None
+
+    def test_find_all_next(self):
+        self.assert_selects(self.start.find_all_next("b"), ["Two", "Three"])
+        self.start.find_all_next(id=3)
+        self.assert_selects(self.start.find_all_next(id=3), ["Three"])
+
+    def test_find_next(self):
+        assert self.start.find_next("b")["id"] == "2"
+        assert self.start.find_next(string="Three") == "Three"
+
+    def test_find_next_for_text_element(self):
+        text = self.tree.find(string="One")
+        assert text.find_next("b").string == "Two"
+        self.assert_selects(text.find_all_next("b"), ["Two", "Three"])
+
+    def test_next_generators(self):
+        start = self.tree.find(string="Two")
+        successors = [node for node in start.next_elements]
+        # There are two successors: the final <b> tag and its text contents.
+        tag, contents = successors
+        assert tag["id"] == "3"
+        assert contents == "Three"
+
+        successors2 = [node for node in start.self_and_next_elements]
+        assert successors2[1:] == successors
+        assert successors2[0] == start
+
+
+class TestPreviousOperations(ProximityTest):
+    def setup_method(self) -> None:
+        super(TestPreviousOperations, self).setup_method()
+        self.end = self.tree.find(string="Three")
+
+    def test_previous(self):
+        assert self.end.previous_element["id"] == "3"
+        assert self.end.previous_element.previous_element == "Two"
+
+    def test_previous_of_first_item_is_none(self):
+        first = self.tree.find("html")
+        assert first.previous_element is None
+
+    def test_previous_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        assert self.tree.previous_element is None
+
+    def test_find_all_previous(self):
+        # The <b> tag containing the "Three" node is the predecessor
+        # of the "Three" node itself, which is why "Three" shows up
+        # here.
+        self.assert_selects(self.end.find_all_previous("b"), ["Three", "Two", "One"])
+        self.assert_selects(self.end.find_all_previous(id=1), ["One"])
+
+    def test_find_previous(self):
+        assert self.end.find_previous("b")["id"] == "3"
+        assert self.end.find_previous(string="One") == "One"
+
+    def test_find_previous_for_text_element(self):
+        text = self.tree.find(string="Three")
+        assert text.find_previous("b").string == "Three"
+        self.assert_selects(text.find_all_previous("b"), ["Three", "Two", "One"])
+
+    def test_previous_generators(self):
+        start = self.tree.find("b", string="One")
+        self.assert_selects_ids(start.previous_elements, ["bodytag", "headtag", 'start'])
+        self.assert_selects_ids(start.self_and_previous_elements, ["1", "bodytag", "headtag", "start"])
+
+
+class SiblingTest(SoupTest):
+    def setup_method(self) -> None:
+        markup = """<html>
+                    <span id="1">
+                     <span id="1.1"></span>
+                    </span>
+                    <span id="2">
+                     <span id="2.1"></span>
+                    </span>
+                    <span id="3">
+                     <span id="3.1"></span>
+                    </span>
+                    <span id="4"></span>
+                    </html>"""
+        # All that whitespace looks good but makes the tests more
+        # difficult. Get rid of it.
+        markup = re.compile(r"\n\s*").sub("", markup)
+        self.tree = self.soup(markup)
+
+
+class TestNextSibling(SiblingTest):
+    def setup_method(self) -> None:
+        super(TestNextSibling, self).setup_method()
+        self.start = self.tree.find(id="1")
+
+    def test_next_sibling_of_root_is_none(self):
+        assert self.tree.next_sibling is None
+
+    def test_next_sibling(self):
+        assert self.start.next_sibling["id"] == "2"
+        assert self.start.next_sibling.next_sibling["id"] == "3"
+
+        # Note the difference between next_sibling and next_element.
+        assert self.start.next_element["id"] == "1.1"
+
+    def test_next_sibling_may_not_exist(self):
+        assert self.tree.html.next_sibling is None
+
+        nested_span = self.tree.find(id="1.1")
+        assert nested_span.next_sibling is None
+
+        last_span = self.tree.find(id="4")
+        assert last_span.next_sibling is None
+
+    def test_find_next_sibling(self):
+        assert self.start.find_next_sibling("span")["id"] == "2"
+
+    def test_next_siblings(self):
+        self.assert_selects_ids(self.start.find_next_siblings("span"), ["2", "3", "4"])
+
+        self.assert_selects_ids(self.start.find_next_siblings(id="3"), ["3"])
+
+    def test_next_siblings_generators(self):
+        self.assert_selects_ids(self.start.next_siblings, ["2", "3", "4"])
+        self.assert_selects_ids(self.start.self_and_next_siblings, ["1", "2", "3", "4"])
+
+    def test_next_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(string="Foo")
+        assert start.next_sibling.name == "b"
+        assert start.next_sibling.next_sibling == "baz"
+
+        self.assert_selects(start.find_next_siblings("b"), ["bar"])
+        assert start.find_next_sibling(string="baz") == "baz"
+        assert start.find_next_sibling(string="nonesuch") is None
+
+
+class TestPreviousSibling(SiblingTest):
+    def setup_method(self) -> None:
+        super(TestPreviousSibling, self).setup_method()
+        self.end = self.tree.find(id="4")
+
+    def test_previous_sibling_of_root_is_none(self):
+        assert self.tree.previous_sibling is None
+
+    def test_previous_sibling(self):
+        assert self.end.previous_sibling["id"] == "3"
+        assert self.end.previous_sibling.previous_sibling["id"] == "2"
+
+        # Note the difference between previous_sibling and previous_element.
+        assert self.end.previous_element["id"] == "3.1"
+
+    def test_previous_sibling_may_not_exist(self):
+        assert self.tree.html.previous_sibling is None
+
+        nested_span = self.tree.find(id="1.1")
+        assert nested_span.previous_sibling is None
+
+        first_span = self.tree.find(id="1")
+        assert first_span.previous_sibling is None
+
+    def test_find_previous_sibling(self):
+        assert self.end.find_previous_sibling("span")["id"] == "3"
+
+    def test_previous_siblings(self):
+        self.assert_selects_ids(
+            self.end.find_previous_siblings("span"), ["3", "2", "1"]
+        )
+
+        self.assert_selects_ids(self.end.find_previous_siblings(id="1"), ["1"])
+
+    def test_previous_siblings_generators(self):
+        self.assert_selects_ids(self.end.previous_siblings, ["3", "2", "1"])
+        self.assert_selects_ids(self.end.self_and_previous_siblings, ["4", "3", "2", "1"])
+
+    def test_previous_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(string="baz")
+        assert start.previous_sibling.name == "b"
+        assert start.previous_sibling.previous_sibling == "Foo"
+
+        self.assert_selects(start.find_previous_siblings("b"), ["bar"])
+        assert start.find_previous_sibling(string="Foo") == "Foo"
+        assert start.find_previous_sibling(string="nonesuch") is None
+
+
+class TestTreeModification(SoupTest):
+    def test_attribute_modification(self):
+        soup = self.soup('<a id="1"></a>')
+        soup.a["id"] = 2
+        assert soup.decode() == self.document_for('<a id="2"></a>')
+        del soup.a["id"]
+        assert soup.decode() == self.document_for("<a></a>")
+        soup.a["id2"] = "foo"
+        assert soup.decode() == self.document_for('<a id2="foo"></a>')
+
+    def test_new_tag_creation(self):
+        builder = builder_registry.lookup("html")()
+        soup = self.soup("<body></body>", builder=builder)
+        a = Tag(soup, builder, "a")
+        ol = Tag(soup, builder, "ol")
+        a["href"] = "http://foo.com/"
+        soup.body.insert(0, a)
+        soup.body.insert(1, ol)
+        assert (
+            soup.body.encode()
+            == b'<body><a href="http://foo.com/"></a><ol></ol></body>'
+        )
+
+    def test_append_to_contents_moves_tag(self):
+        doc = """<p id="1">Don't leave me <b>here</b>.</p>
+                <p id="2">Don\'t leave!</p>"""
+        soup = self.soup(doc)
+        second_para = soup.find(id="2")
+        bold = soup.b
+
+        # Move the <b> tag to the end of the second paragraph.
+        soup.find(id="2").append(soup.b)
+
+        # The <b> tag is now a child of the second paragraph.
+        assert bold.parent == second_para
+
+        assert soup.decode() == self.document_for(
+            '<p id="1">Don\'t leave me .</p>\n' '<p id="2">Don\'t leave!<b>here</b></p>'
+        )
+
+    def test_insertion_returns_inserted_things(self):
+        soup = self.soup("<html></html>")
+        html = soup.find('html')
+        head = html.append(soup.new_tag('head'))
+        assert head.name == 'head'
+
+        [title] = head.insert(0, soup.new_tag('title'))
+        assert title.name == 'title'
+
+        text5 = title.append('5')
+        assert text5 == '5'
+        text34 = text5.insert_before('3', '4')
+        assert text34 == ['3', '4']
+        text67 = text5.insert_after('6', '7')
+        assert text67 == ['6', '7']
+        text89 = title.extend(['8', '9'])
+        assert text89 == ['8', '9']
+        assert title.get_text() == '3456789'
+
+    def test_replace_with_returns_thing_that_was_replaced(self):
+        text = "<a></a><b><c></c></b>"
+        soup = self.soup(text)
+        a = soup.a
+        new_a = a.replace_with(soup.c)
+        assert a == new_a
+
+    def test_unwrap_returns_thing_that_was_replaced(self):
+        text = "<a><b></b><c></c></a>"
+        soup = self.soup(text)
+        a = soup.a
+        new_a = a.unwrap()
+        assert a == new_a
+
+    def test_replace_with_and_unwrap_give_useful_exception_when_tag_has_no_parent(self):
+        soup = self.soup("<a><b>Foo</b></a><c>Bar</c>")
+        a = soup.a
+        a.extract()
+        assert None is a.parent
+        with pytest.raises(ValueError):
+            a.unwrap()
+        with pytest.raises(ValueError):
+            a.replace_with(soup.c)
+
+    def test_replace_tag_with_itself(self):
+        text = "<a><b></b><c>Foo<d></d></c></a><a><e></e></a>"
+        soup = self.soup(text)
+        c = soup.c
+        result = soup.c.replace_with(c)
+        assert result == c
+        assert soup.decode() == self.document_for(text)
+
+    def test_replace_tag_with_its_parent_raises_exception(self):
+        text = "<a><b></b></a>"
+        soup = self.soup(text)
+        with pytest.raises(ValueError):
+            soup.b.replace_with(soup.a)
+
+    def test_insert_tag_into_itself_raises_exception(self):
+        text = "<a><b></b></a>"
+        soup = self.soup(text)
+        with pytest.raises(ValueError):
+            soup.a.insert(0, soup.a)
+
+    def test_insert_multiple_elements(self):
+        soup = self.soup("<p>And now, a word:</p><p>And we're back.</p>")
+        p2, p3 = soup.insert(1, soup.new_tag("p", string="p2"), soup.new_tag("p", string="p3"))
+        assert "p2" == p2.string
+        assert "p3" == p3.string
+
+        p1, p2, p3, p4 = list(soup.children)
+        assert "And now, a word:" == p1.string
+        assert "p2" == p2.string
+        assert "p3" == p3.string
+        assert "And we're back." == p4.string
+
+    def test_insert_beautifulsoup_object_inserts_children(self):
+        """Inserting one BeautifulSoup object into another actually inserts all
+        of its children -- you'll never combine BeautifulSoup objects.
+        """
+        soup = self.soup("<p>And now, a word:</p><p>And we're back.</p>")
+
+        text = "<p>p2</p><p>p3</p>"
+        to_insert = self.soup(text)
+        p2, p3 = soup.insert(1, to_insert)
+        assert "p2" == p2.string
+        assert "p3" == p3.string
+
+        for i in soup.descendants:
+            assert not isinstance(i, BeautifulSoup)
+
+        p1, p2, p3, p4 = list(soup.children)
+        assert "And now, a word:" == p1.string
+        assert "p2" == p2.string
+        assert "p3" == p3.string
+        assert "And we're back." == p4.string
+
+    def test_replace_with_maintains_next_element_throughout(self):
+        soup = self.soup("<p><a>one</a><b>three</b></p>")
+        a = soup.a
+        # Make it so the <a> tag has two text children.
+        a.insert(1, "two")
+
+        # Now replace each one with the empty string.
+        left, right = a.contents
+        left.replace_with("")
+        right.replace_with("")
+
+        # The <b> tag is still connected to the tree.
+        assert "three" == soup.b.string
+
+    def test_replace_final_node(self):
+        soup = self.soup("<b>Argh!</b>")
+        soup.find(string="Argh!").replace_with("Hooray!")
+        new_text = soup.find(string="Hooray!")
+        b = soup.b
+        assert new_text.previous_element == b
+        assert new_text.parent == b
+        assert new_text.previous_element.next_element == new_text
+        assert new_text.next_element is None
+
+    def test_consecutive_text_nodes(self):
+        # A builder should never create two consecutive text nodes,
+        # but if you insert one next to another, Beautiful Soup will
+        # handle it correctly.
+        soup = self.soup("<a><b>Argh!</b><c></c></a>")
+        soup.b.insert(1, "Hooray!")
+
+        assert soup.decode() == self.document_for("<a><b>Argh!Hooray!</b><c></c></a>")
+
+        new_text = soup.find(string="Hooray!")
+        assert new_text.previous_element == "Argh!"
+        assert new_text.previous_element.next_element == new_text
+
+        assert new_text.previous_sibling == "Argh!"
+        assert new_text.previous_sibling.next_sibling == new_text
+
+        assert new_text.next_sibling is None
+        assert new_text.next_element == soup.c
+
+    def test_insert_string(self):
+        soup = self.soup("<a></a>")
+        soup.a.insert(0, "bar")
+        soup.a.insert(0, "foo")
+        # The string were added to the tag.
+        assert ["foo", "bar"] == soup.a.contents
+        # And they were converted to NavigableStrings.
+        assert soup.a.contents[0].next_element == "bar"
+
+    def test_append(self):
+        soup = self.soup("<b>1</b>")
+        result = soup.b.append("2")
+        assert result == "2"
+        assert soup.b.decode() == "<b>12</b>"
+
+    def test_insert_tag(self):
+        builder = self.default_builder()
+        soup = self.soup("<a><b>Find</b><c>lady!</c><d></d></a>", builder=builder)
+        magic_tag = Tag(soup, builder, "magictag")
+        magic_tag.insert(0, "the")
+        soup.a.insert(1, magic_tag)
+
+        assert soup.decode() == self.document_for(
+            "<a><b>Find</b><magictag>the</magictag><c>lady!</c><d></d></a>"
+        )
+
+        # Make sure all the relationships are hooked up correctly.
+        b_tag = soup.b
+        assert b_tag.next_sibling == magic_tag
+        assert magic_tag.previous_sibling == b_tag
+
+        find = b_tag.find(string="Find")
+        assert find.next_element == magic_tag
+        assert magic_tag.previous_element == find
+
+        c_tag = soup.c
+        assert magic_tag.next_sibling == c_tag
+        assert c_tag.previous_sibling == magic_tag
+
+        the = magic_tag.find(string="the")
+        assert the.parent == magic_tag
+        assert the.next_element == c_tag
+        assert c_tag.previous_element == the
+
+    def test_insert_into_the_current_location(self):
+        data = "<a>b<c></c>d</a>"
+        soup = self.soup(data)
+        soup.a.insert(1, soup.c)
+        assert data == soup.decode()
+
+    def test_append_child_thats_already_at_the_end(self):
+        data = "<a><b></b></a>"
+        soup = self.soup(data)
+        soup.a.append(soup.b)
+        assert data == soup.decode()
+
+    def test_extend_with_a_list_of_elements(self):
+        data = "<a><b><c><d><e><f><g></g></f></e></d></c></b></a>"
+        soup = self.soup(data)
+        elements = [soup.g, soup.f, soup.e, soup.d, soup.c, soup.b]
+        soup.a.extend(elements)
+        assert "<a><g></g><f></f><e></e><d></d><c></c><b></b></a>" == soup.decode()
+
+    def test_extend_with_a_list_of_strings(self):
+        data = "<a></a>"
+        soup = self.soup(data)
+        elements = ["b", "c", NavigableString("d"), "e"]
+        soup.a.extend(elements)
+        assert "<a>bcde</a>" == soup.decode()
+
+    @pytest.mark.parametrize("get_tags", [lambda tag: tag, lambda tag: tag.contents])
+    def test_extend_with_another_tags_contents(self, get_tags):
+        data = '<body><div id="d1"><a>1</a><a>2</a><a>3</a><a>4</a></div><div id="d2"></div></body>'
+        soup = self.soup(data)
+        d1 = soup.find("div", id="d1")
+        d2 = soup.find("div", id="d2")
+        tags = get_tags(d1)
+        d2.extend(tags)
+        assert '<div id="d1"></div>' == d1.decode()
+        assert '<div id="d2"><a>1</a><a>2</a><a>3</a><a>4</a></div>' == d2.decode()
+
+    @pytest.mark.parametrize(
+        "string_source,result",
+        (
+            [lambda soup: soup.a.string, "<a></a><b>1</b>"],
+            [lambda soup: "abcde", "<a>1</a><b>abcde</b>"],
+        ),
+    )
+    def test_extend_with_a_single_non_tag_element(self, string_source, result):
+        data = "<div><a>1</a><b></b></div>"
+        soup = self.soup(data)
+        with warnings.catch_warnings(record=True) as w:
+            string = string_source(soup)
+            soup.b.extend(string)
+            assert soup.div.decode_contents() == result
+            [warning] = w
+            assert warning.filename == __file__
+            msg = str(warning.message)
+            assert (
+                msg
+                == "A single non-Tag item was passed into Tag.extend. Use Tag.append instead."
+            )
+
+    def test_move_tag_to_beginning_of_parent(self):
+        data = "<a><b></b><c></c><d></d></a>"
+        soup = self.soup(data)
+        soup.a.insert(0, soup.d)
+        assert "<a><d></d><b></b><c></c></a>" == soup.decode()
+
+    def test_insert_works_on_empty_element_tag(self):
+        # This is a little strange, since most HTML parsers don't allow
+        # markup like this to come through. But in general, we don't
+        # know what the parser would or wouldn't have allowed, so
+        # I'm letting this succeed for now.
+        soup = self.soup("<br/>")
+        soup.br.insert(1, "Contents")
+        assert str(soup.br) == "<br>Contents</br>"
+
+    def test_insert_before(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_before("BAZ")
+        soup.a.insert_before("QUUX")
+        assert soup.decode() == self.document_for("QUUX<a>foo</a>BAZ<b>bar</b>")
+
+        soup.a.insert_before(soup.b)
+        assert soup.decode() == self.document_for("QUUX<b>bar</b><a>foo</a>BAZ")
+
+        # Can't insert an element before itself.
+        b = soup.b
+        with pytest.raises(ValueError):
+            b.insert_before(b)
+
+        # Can't insert before if an element has no parent.
+        b.extract()
+        with pytest.raises(ValueError):
+            b.insert_before("nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+
+        # TODO: OK but what happens?
+
+    def test_insert_multiple_before(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_before("BAZ", " ", "QUUX")
+        soup.a.insert_before("QUUX", " ", "BAZ")
+        assert soup.decode() == self.document_for(
+            "QUUX BAZ<a>foo</a>BAZ QUUX<b>bar</b>"
+        )
+
+        soup.a.insert_before(soup.b, "FOO")
+        assert soup.decode() == self.document_for(
+            "QUUX BAZ<b>bar</b>FOO<a>foo</a>BAZ QUUX"
+        )
+
+    def test_insert_after(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_after("BAZ")
+        soup.a.insert_after("QUUX")
+        assert soup.decode() == self.document_for("<a>foo</a>QUUX<b>bar</b>BAZ")
+        soup.b.insert_after(soup.a)
+        assert soup.decode() == self.document_for("QUUX<b>bar</b><a>foo</a>BAZ")
+
+        # Can't insert an element after itself.
+        b = soup.b
+        with pytest.raises(ValueError):
+            b.insert_after(b)
+
+        # Can't insert after if an element has no parent.
+        b.extract()
+        with pytest.raises(ValueError):
+            b.insert_after("nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+
+        # TODO: OK but what does it look like?
+
+    def test_insert_multiple_after(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        soup.b.insert_after("BAZ", " ", "QUUX")
+        soup.a.insert_after("QUUX", " ", "BAZ")
+        assert soup.decode() == self.document_for(
+            "<a>foo</a>QUUX BAZ<b>bar</b>BAZ QUUX"
+        )
+        soup.b.insert_after(soup.a, "FOO ")
+        assert soup.decode() == self.document_for(
+            "QUUX BAZ<b>bar</b><a>foo</a>FOO BAZ QUUX"
+        )
+
+    def test_insert_after_raises_exception_if_after_has_no_meaning(self):
+        soup = self.soup("")
+        tag = soup.new_tag("a")
+        string = soup.new_string("")
+        with pytest.raises(ValueError):
+            string.insert_after(tag)
+        with pytest.raises(NotImplementedError):
+            soup.insert_after(tag)
+        with pytest.raises(ValueError):
+            tag.insert_after(tag)
+
+    def test_insert_before_raises_notimplementederror_if_before_has_no_meaning(self):
+        soup = self.soup("")
+        tag = soup.new_tag("a")
+        string = soup.new_string("")
+        with pytest.raises(ValueError):
+            string.insert_before(tag)
+        with pytest.raises(NotImplementedError):
+            soup.insert_before(tag)
+        with pytest.raises(ValueError):
+            tag.insert_before(tag)
+
+    def test_replace_with(self):
+        soup = self.soup("<p>There's <b>no</b> business like <b>show</b> business</p>")
+        no, show = soup.find_all("b")
+        show.replace_with(no)
+        assert soup.decode() == self.document_for(
+            "<p>There's  business like <b>no</b> business</p>"
+        )
+
+        assert show.parent is None
+        assert no.parent == soup.p
+        assert no.next_element == "no"
+        assert no.next_sibling == " business"
+
+    def test_replace_with_errors(self):
+        # Can't replace a tag that's not part of a tree.
+        a_tag = Tag(name="a")
+        with pytest.raises(ValueError):
+            a_tag.replace_with("won't work")
+
+        # Can't replace a tag with its parent.
+        a_tag = self.soup("<a><b></b></a>").a
+        with pytest.raises(ValueError):
+            a_tag.b.replace_with(a_tag)
+
+        # Or with a list that includes its parent.
+        with pytest.raises(ValueError):
+            a_tag.b.replace_with("string1", a_tag, "string2")
+
+    def test_replace_with_multiple(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        d_tag = soup.new_tag("d")
+        d_tag.string = "Text In D Tag"
+        e_tag = soup.new_tag("e")
+        f_tag = soup.new_tag("f")
+        a_string = "Random Text"
+        soup.c.replace_with(d_tag, e_tag, a_string, f_tag)
+        assert (
+            soup.decode()
+            == "<a><b></b><d>Text In D Tag</d><e></e>Random Text<f></f></a>"
+        )
+        assert soup.b.next_element == d_tag
+        assert d_tag.string.next_element == e_tag
+        assert e_tag.next_element.string == a_string
+        assert e_tag.next_element.next_element == f_tag
+
+    def test_replace_first_child(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        soup.b.replace_with(soup.c)
+        assert "<a><c></c></a>" == soup.decode()
+
+    def test_replace_last_child(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        soup.c.replace_with(soup.b)
+        assert "<a><b></b></a>" == soup.decode()
+
+    def test_nested_tag_replace_with(self):
+        soup = self.soup(
+            """<a>We<b>reserve<c>the</c><d>right</d></b></a><e>to<f>refuse</f><g>service</g></e>"""
+        )
+
+        # Replace the entire <b> tag and its contents ("reserve the
+        # right") with the <f> tag ("refuse").
+        remove_tag = soup.b
+        move_tag = soup.f
+        remove_tag.replace_with(move_tag)
+
+        assert soup.decode() == self.document_for(
+            "<a>We<f>refuse</f></a><e>to<g>service</g></e>"
+        )
+
+        # The <b> tag is now an orphan.
+        assert remove_tag.parent is None
+        assert remove_tag.find(string="right").next_element is None
+        assert remove_tag.previous_element is None
+        assert remove_tag.next_sibling is None
+        assert remove_tag.previous_sibling is None
+
+        # The <f> tag is now connected to the <a> tag.
+        assert move_tag.parent == soup.a
+        assert move_tag.previous_element == "We"
+        assert move_tag.next_element.next_element == soup.e
+        assert move_tag.next_sibling is None
+
+        # The gap where the <f> tag used to be has been mended, and
+        # the word "to" is now connected to the <g> tag.
+        to_text = soup.find(string="to")
+        g_tag = soup.g
+        assert to_text.next_element == g_tag
+        assert to_text.next_sibling == g_tag
+        assert g_tag.previous_element == to_text
+        assert g_tag.previous_sibling == to_text
+
+    def test_unwrap(self):
+        tree = self.soup("""
+            <p>Unneeded <em>formatting</em> is unneeded</p>
+            """)
+        tree.em.unwrap()
+        assert tree.em is None
+        assert tree.p.text == "Unneeded formatting is unneeded"
+
+    def test_wrap(self):
+        soup = self.soup("I wish I was bold.")
+        value = soup.string.wrap(soup.new_tag("b"))
+        assert value.decode() == "<b>I wish I was bold.</b>"
+        assert soup.decode() == self.document_for("<b>I wish I was bold.</b>")
+
+    def test_wrap_extracts_tag_from_elsewhere(self):
+        soup = self.soup("<b></b>I wish I was bold.")
+        soup.b.next_sibling.wrap(soup.b)
+        assert soup.decode() == self.document_for("<b>I wish I was bold.</b>")
+
+    def test_wrap_puts_new_contents_at_the_end(self):
+        soup = self.soup("<b>I like being bold.</b>I wish I was bold.")
+        soup.b.next_sibling.wrap(soup.b)
+        assert 2 == len(soup.b.contents)
+        assert soup.decode() == self.document_for(
+            "<b>I like being bold.I wish I was bold.</b>"
+        )
+
+    def test_extract(self):
+        soup = self.soup(
+            '<html><body>Some content. <div id="nav">Nav crap</div> More content.</body></html>'
+        )
+
+        assert len(soup.body.contents) == 3
+        extracted = soup.find(id="nav").extract()
+
+        assert soup.decode() == "<html><body>Some content.  More content.</body></html>"
+        assert extracted.decode() == '<div id="nav">Nav crap</div>'
+
+        # The extracted tag is now an orphan.
+        assert len(soup.body.contents) == 2
+        assert extracted.parent is None
+        assert extracted.previous_element is None
+        assert extracted.next_element.next_element is None
+
+        # The gap where the extracted tag used to be has been mended.
+        content_1 = soup.find(string="Some content. ")
+        content_2 = soup.find(string=" More content.")
+        assert content_1.next_element == content_2
+        assert content_1.next_sibling == content_2
+        assert content_2.previous_element == content_1
+        assert content_2.previous_sibling == content_1
+
+    def test_extract_distinguishes_between_identical_strings(self):
+        soup = self.soup("<a>foo</a><b>bar</b>")
+        foo_1 = soup.a.string
+        foo_2 = soup.new_string("foo")
+        bar_2 = soup.new_string("bar")
+        soup.a.append(foo_2)
+        soup.b.append(bar_2)
+
+        # Now there are two identical strings in the <a> tag, and two
+        # in the <b> tag. Let's remove the first "foo" and the second
+        # "bar".
+        foo_1.extract()
+        bar_2.extract()
+        assert foo_2 == soup.a.string
+        assert bar_2 == soup.b.string
+
+    def test_extract_multiples_of_same_tag(self):
+        soup = self.soup("""
+<html>
+<head>
+<script>foo</script>
+</head>
+<body>
+ <script>bar</script>
+ <a></a>
+</body>
+<script>baz</script>
+</html>""")
+        [soup.script.extract() for i in soup.find_all("script")]
+        assert "<body>\n\n<a></a>\n</body>" == str(soup.body)
+
+    def test_extract_works_when_element_is_surrounded_by_identical_strings(self):
+        soup = self.soup("<html>\n" "<body>hi</body>\n" "</html>")
+        soup.find("body").extract()
+        assert None is soup.find("body")
+
+    def test_clear(self):
+        """Tag.clear()"""
+        soup = self.soup("<p><a>String <em>Italicized</em></a> and another</p>")
+        # clear using extract()
+        a = soup.a
+        soup.p.clear()
+        assert len(soup.p.contents) == 0
+        assert hasattr(a, "contents")
+
+        # clear using decompose()
+        em = a.em
+        a.clear(decompose=True)
+        assert 0 == len(em.contents)
+
+    @pytest.mark.parametrize(
+        "method_name,expected_result",
+        [
+            (
+                "descendants",
+                '<div><em>child1</em><p id="start"></p><p>child3</p></div>',
+            ),
+            (
+                "next_siblings",
+                '<div><em>child1</em><p id="start"><a>Second <em>child</em></a></p></div>',
+            ),
+            # Confused about why child3 is still here in this test? It's because removing the <p id="start"> tag from the tree removes all of its children from the tree as well. 'child'.next_element becomes None, because 'child' is no longer in the tree, and iteration stops there. Don't do this kind of thing, is what I'm saying.
+            (
+                "next_elements",
+                '<div><em>child1</em><p id="start"></p><p>child3</p></div>',
+            ),
+            ("children", '<div><em>child1</em><p id="start"></p><p>child3</p></div>'),
+            ("previous_elements", ""),
+            (
+                "previous_siblings",
+                '<div><p id="start"><a>Second <em>child</em></a></p><p>child3</p></div>',
+            ),
+            ("parents", ""),
+        ],
+    )
+    def test_extract_during_iteration(self, method_name, expected_result):
+        # The iterators should be able to proceed even if the most
+        # current yield got removed from the tree. This kind of code
+        # is a bad idea, but we should be able to run it without an exception.
+        soup = self.soup(
+            "<div><em>child1</em><p id='start'><a>Second <em>child</em></a></p><p>child3</p></div>"
+        )
+        iterator = getattr(soup.p, method_name)
+        for i in iterator:
+            i.extract()
+        assert expected_result == soup.decode()
+
+    def test_decompose(self):
+        # Test PageElement.decompose() and PageElement.decomposed
+        soup = self.soup("<p><a>String <em>Italicized</em></a></p><p>Another para</p>")
+        p1, p2 = soup.find_all("p")
+        a = p1.a
+        text = p1.em.string
+        for i in [p1, p2, a, text]:
+            assert False is i.decomposed
+
+        # This sets p1 and everything beneath it to decomposed.
+        p1.decompose()
+        for i in [p1, a, text]:
+            assert True is i.decomposed
+        # p2 is unaffected.
+        assert False is p2.decomposed
+
+    def test_decompose_string(self):
+        soup = self.soup("<div><p>String 1</p><p>String 2</p></p>")
+        div = soup.div
+        text = div.p.string
+        assert False is text.decomposed
+        text.decompose()
+        assert True is text.decomposed
+        assert "<div><p></p><p>String 2</p></div>" == div.decode()
+
+    def test_string_set(self):
+        """Tag.string = 'string'"""
+        soup = self.soup("<a></a> <b><c></c></b>")
+        soup.a.string = "foo"
+        assert soup.a.contents == ["foo"]
+        soup.b.string = "bar"
+        assert soup.b.contents == ["bar"]
+
+    def test_string_set_does_not_affect_original_string(self):
+        soup = self.soup("<a><b>foo</b><c>bar</c>")
+        soup.b.string = soup.c.string
+        assert soup.a.encode() == b"<a><b>bar</b><c>bar</c></a>"
+
+    def test_set_string_preserves_class_of_string(self):
+        soup = self.soup("<a></a>")
+        cdata = CData("foo")
+        soup.a.string = cdata
+        assert isinstance(soup.a.string, CData)
+
+
+all_find_type_methods = [
+    "find",
+    "find_all",
+    "find_parent",
+    "find_parents",
+    "find_next",
+    "find_all_next",
+    "find_previous",
+    "find_all_previous",
+    "find_next_sibling",
+    "find_next_siblings",
+    "find_previous_sibling",
+    "find_previous_siblings",
+]
+
+
+class TestDeprecatedArguments(SoupTest):
+    @pytest.mark.parametrize("method_name", all_find_type_methods)
+    def test_find_type_method_string(self, method_name):
+        soup = self.soup("<a>some</a><b>markup</b>")
+        method = getattr(soup.b, method_name)
+        with warnings.catch_warnings(record=True) as w:
+            method(text="markup")
+            [warning] = w
+            assert warning.filename == __file__
+            msg = str(warning.message)
+            assert (
+                msg
+                == "The 'text' argument to find()-type methods is deprecated. Use 'string' instead."
+            )
+
+
+class TestWarnings(SoupTest):
+    @pytest.mark.parametrize("method_name", all_find_type_methods)
+    def test_suspicious_syntax_warning(self, method_name):
+        soup = self.soup("<a>some</a><b>markup</b>")
+        method = getattr(soup.b, method_name)
+        with warnings.catch_warnings(record=True) as w:
+            method(_class="u")
+            [warning] = w
+            assert warning.filename == __file__
+            assert isinstance(warning.message, AttributeResemblesVariableWarning)
+            msg = str(warning.message)
+            assert (
+                "'_class' is an unusual attribute name and is a common misspelling for 'class_'"
+                in msg
+            )