diff env/lib/python3.7/site-packages/bs4/tests/test_tree.py @ 0:26e78fe6e8c4 draft

"planemo upload commit c699937486c35866861690329de38ec1a5d9f783"
author shellac
date Sat, 02 May 2020 07:14:21 -0400
parents
children
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.7/site-packages/bs4/tests/test_tree.py	Sat May 02 07:14:21 2020 -0400
@@ -0,0 +1,2323 @@
+# -*- 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.
+"""
+
+from pdb import set_trace
+import copy
+import pickle
+import re
+import warnings
+from bs4 import BeautifulSoup
+from bs4.builder import (
+    builder_registry,
+    HTMLParserTreeBuilder,
+)
+from bs4.element import (
+    PY3K,
+    CData,
+    Comment,
+    Declaration,
+    Doctype,
+    Formatter,
+    NavigableString,
+    Script,
+    SoupStrainer,
+    Stylesheet,
+    Tag,
+    TemplateString,
+)
+from bs4.testing import (
+    SoupTest,
+    skipIf,
+)
+
+XML_BUILDER_PRESENT = (builder_registry.lookup("xml") is not None)
+LXML_PRESENT = (builder_registry.lookup("lxml") is not None)
+
+class TreeTest(SoupTest):
+
+    def assertSelects(self, tags, should_match):
+        """Make sure that the given tags have the correct text.
+
+        This is used in tests that define a bunch of tags, each
+        containing a single string, and then select certain strings by
+        some mechanism.
+        """
+        self.assertEqual([tag.string for tag in tags], should_match)
+
+    def assertSelectsIDs(self, tags, should_match):
+        """Make sure that the given tags have the correct IDs.
+
+        This is used in tests that define a bunch of tags, each
+        containing a single string, and then select certain strings by
+        some mechanism.
+        """
+        self.assertEqual([tag['id'] for tag in tags], should_match)
+
+
+class TestFind(TreeTest):
+    """Basic tests of the find() method.
+
+    find() just calls find_all() with limit=1, so it's not tested all
+    that thouroughly here.
+    """
+
+    def test_find_tag(self):
+        soup = self.soup("<a>1</a><b>2</b><a>3</a><b>4</b>")
+        self.assertEqual(soup.find("b").string, "2")
+
+    def test_unicode_text_find(self):
+        soup = self.soup('<h1>Räksmörgås</h1>')
+        self.assertEqual(soup.find(string='Räksmörgås'), 'Räksmörgås')
+
+    def test_unicode_attribute_find(self):
+        soup = self.soup('<h1 id="Räksmörgås">here it is</h1>')
+        str(soup)
+        self.assertEqual("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>")
+        self.assertEqual(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>")
+        self.assertEqual(2, len(soup.find_all('a')))
+
+class TestFindAll(TreeTest):
+    """Basic tests of the find_all() method."""
+
+    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.
+        self.assertEqual(soup.find_all(string="bar"), ["bar"])
+        self.assertEqual(soup.find_all(text="bar"), ["bar"])
+        # Match any of a number of strings.
+        self.assertEqual(
+            soup.find_all(text=["Foo", "bar"]), ["Foo", "bar"])
+        # Match a regular expression.
+        self.assertEqual(soup.find_all(text=re.compile('.*')),
+                         ["Foo", "bar", '\xbb'])
+        # Match anything.
+        self.assertEqual(soup.find_all(text=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.assertSelects(soup.find_all('a', limit=3), ["1", "2", "3"])
+        self.assertSelects(soup.find_all('a', limit=1), ["1"])
+        self.assertSelects(
+            soup.find_all('a', limit=10), ["1", "2", "3", "4", "5"])
+
+        # A limit of 0 means no limit.
+        self.assertSelects(
+            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.assertSelects(soup('a', limit=1), ["1"])
+        self.assertSelects(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.
+        l = []
+        l.append(l)
+
+        # Without special code in _normalize_search_value, this would cause infinite
+        # recursion.
+        self.assertEqual([], soup.find_all(l))
+
+    def test_find_all_resultset(self):
+        """All find_all calls return a ResultSet"""
+        soup = self.soup("<a></a>")
+        result = soup.find_all("a")
+        self.assertTrue(hasattr(result, "source"))
+
+        result = soup.find_all(True)
+        self.assertTrue(hasattr(result, "source"))
+
+        result = soup.find_all(text="foo")
+        self.assertTrue(hasattr(result, "source"))
+
+
+class TestFindAllBasicNamespaces(TreeTest):
+
+    def test_find_by_namespaced_name(self):
+        soup = self.soup('<mathml:msqrt>4</mathml:msqrt><a svg:fill="red">')
+        self.assertEqual("4", soup.find("mathml:msqrt").string)
+        self.assertEqual("a", soup.find(attrs= { "svg:fill" : "red" }).name)
+
+
+class TestFindAllByName(TreeTest):
+    """Test ways of finding tags by tag name."""
+
+    def setUp(self):
+        super(TreeTest, self).setUp()
+        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.assertSelects(
+            self.tree.find_all('a'), ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_name_and_text(self):
+        self.assertSelects(
+            self.tree.find_all('a', text='First tag.'), ['First tag.'])
+
+        self.assertSelects(
+            self.tree.find_all('a', text=True), ['First tag.', 'Nested tag.'])
+
+        self.assertSelects(
+            self.tree.find_all('a', text=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.assertSelects(self.tree.c.find_all('a'), ['Nested tag.'])
+
+    def test_calling_element_invokes_find_all(self):
+        self.assertSelects(self.tree('a'), ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_strainer(self):
+        self.assertSelects(
+            self.tree.find_all(SoupStrainer('a')),
+            ['First tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_names(self):
+        self.assertSelects(
+            self.tree.find_all(['a', 'b']),
+            ['First tag.', 'Second tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_dict(self):
+        self.assertSelects(
+            self.tree.find_all({'a' : True, 'b' : True}),
+            ['First tag.', 'Second tag.', 'Nested tag.'])
+
+    def test_find_all_by_tag_re(self):
+        self.assertSelects(
+            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.assertSelects(
+            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']);
+        self.assertEqual('3', r1.string)
+        self.assertEqual('3', r2.string)
+        self.assertEqual('1', r3.string)
+        self.assertEqual('3', r4.string)
+
+        
+class TestFindAllByAttribute(TreeTest):
+
+    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.assertSelects(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)
+        self.assertEqual([soup.a], soup.find_all(title=peace))
+        self.assertEqual([soup.a], soup.find_all(title=peace.decode("utf8")))
+        self.assertEqual([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.assertSelects(tree.find_all(name='name1'),
+                           ["A tag called 'name1'."])
+        # This does what you want.
+        self.assertSelects(tree.find_all(attrs={'name' : 'name1'}),
+                           ["Name match."])
+
+        self.assertSelects(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.assertSelects(tree.find_all('a', class_='1'), ['Class 1.'])
+        self.assertSelects(tree.find_all('c', class_='3'), ['Class 3 and 4.'])
+        self.assertSelects(tree.find_all('c', class_='4'), ['Class 3 and 4.'])
+
+        # Passing in a string to 'attrs' will also search the CSS class.
+        self.assertSelects(tree.find_all('a', '1'), ['Class 1.'])
+        self.assertSelects(tree.find_all(attrs='1'), ['Class 1.', 'Class 1.'])
+        self.assertSelects(tree.find_all('c', '3'), ['Class 3 and 4.'])
+        self.assertSelects(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.assertSelects(f, ["Found it"])
+
+        f = tree.find_all("gar", class_=re.compile("a"))
+        self.assertSelects(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.assertSelects(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.assertSelects(soup.find_all("a", re.compile("ba")), ["Found it"])
+
+        def big_attribute_value(value):
+            return len(value) > 3
+
+        self.assertSelects(soup.find_all("a", big_attribute_value), [])
+
+        def small_attribute_value(value):
+            return len(value) <= 3
+
+        self.assertSelects(
+            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")
+        self.assertEqual([a, a2], soup.find_all("a", "foo"))
+        self.assertEqual([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.
+        self.assertEqual([a], soup.find_all("a", class_="foo bar"))
+        self.assertEqual([a], soup.find_all("a", "foo bar"))
+        self.assertEqual([], 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.assertSelects(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.assertSelects(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.assertSelects(
+            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.assertSelects(tree.find_all(id=1), expected)
+        self.assertSelects(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.assertSelects(tree.find_all(id=["1", "3", "4"]),
+                           ["1", "3"])
+
+    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.assertSelects(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
+
+        self.assertEqual([a], soup.find_all("a", text="foo"))
+        self.assertEqual([], soup.find_all("a", text="bar"))
+        self.assertEqual([], soup.find_all("a", text="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>")
+        self.assertEqual(soup.find_all("a"), soup.find_all("a", text="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
+
+        self.assertEqual([a], soup.find_all(id=2, text="foo"))
+        self.assertEqual([], soup.find_all(id=1, text="bar"))
+
+
+class TestSmooth(TreeTest):
+    """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.
+        self.assertEqual(None, div.span.string)
+
+        self.assertEqual(7, len(div.contents))
+        div.smooth()
+        self.assertEqual(5, len(div.contents))
+
+        # The three strings at the beginning of div.contents have been
+        # merged into on string.
+        #
+        self.assertEqual('abc', div.contents[0])
+
+        # The call is recursive -- the <span> tag was also smoothed.
+        self.assertEqual('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.
+        self.assertEqual('Comment 1', div.contents[1])
+        self.assertEqual('Comment 2', div.contents[2])
+
+
+class TestIndex(TreeTest):
+    """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):
+            self.assertEqual(i, div.index(element))
+        self.assertRaises(ValueError, tree.index, 1)
+
+
+class TestParentOperations(TreeTest):
+    """Test navigation and searching through an element's parents."""
+
+    def setUp(self):
+        super(TestParentOperations, self).setUp()
+        self.tree = self.soup('''<ul id="empty"></ul>
+                                 <ul id="top">
+                                  <ul id="middle">
+                                   <ul id="bottom">
+                                    <b>Start here</b>
+                                   </ul>
+                                  </ul>''')
+        self.start = self.tree.b
+
+
+    def test_parent(self):
+        self.assertEqual(self.start.parent['id'], 'bottom')
+        self.assertEqual(self.start.parent.parent['id'], 'middle')
+        self.assertEqual(self.start.parent.parent.parent['id'], 'top')
+
+    def test_parent_of_top_tag_is_soup_object(self):
+        top_tag = self.tree.contents[0]
+        self.assertEqual(top_tag.parent, self.tree)
+
+    def test_soup_object_has_no_parent(self):
+        self.assertEqual(None, self.tree.parent)
+
+    def test_find_parents(self):
+        self.assertSelectsIDs(
+            self.start.find_parents('ul'), ['bottom', 'middle', 'top'])
+        self.assertSelectsIDs(
+            self.start.find_parents('ul', id="middle"), ['middle'])
+
+    def test_find_parent(self):
+        self.assertEqual(self.start.find_parent('ul')['id'], 'bottom')
+        self.assertEqual(self.start.find_parent('ul', id='top')['id'], 'top')
+
+    def test_parent_of_text_element(self):
+        text = self.tree.find(text="Start here")
+        self.assertEqual(text.parent.name, 'b')
+
+    def test_text_element_find_parent(self):
+        text = self.tree.find(text="Start here")
+        self.assertEqual(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]
+        self.assertEqual(parents, ['bottom', 'middle', 'top'])
+
+
+class ProximityTest(TreeTest):
+
+    def setUp(self):
+        super(TreeTest, self).setUp()
+        self.tree = self.soup(
+            '<html id="start"><head></head><body><b id="1">One</b><b id="2">Two</b><b id="3">Three</b></body></html>')
+
+
+class TestNextOperations(ProximityTest):
+
+    def setUp(self):
+        super(TestNextOperations, self).setUp()
+        self.start = self.tree.b
+
+    def test_next(self):
+        self.assertEqual(self.start.next_element, "One")
+        self.assertEqual(self.start.next_element.next_element['id'], "2")
+
+    def test_next_of_last_item_is_none(self):
+        last = self.tree.find(text="Three")
+        self.assertEqual(last.next_element, None)
+
+    def test_next_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        self.assertEqual(self.tree.next_element, None)
+
+    def test_find_all_next(self):
+        self.assertSelects(self.start.find_all_next('b'), ["Two", "Three"])
+        self.start.find_all_next(id=3)
+        self.assertSelects(self.start.find_all_next(id=3), ["Three"])
+
+    def test_find_next(self):
+        self.assertEqual(self.start.find_next('b')['id'], '2')
+        self.assertEqual(self.start.find_next(text="Three"), "Three")
+
+    def test_find_next_for_text_element(self):
+        text = self.tree.find(text="One")
+        self.assertEqual(text.find_next("b").string, "Two")
+        self.assertSelects(text.find_all_next("b"), ["Two", "Three"])
+
+    def test_next_generator(self):
+        start = self.tree.find(text="Two")
+        successors = [node for node in start.next_elements]
+        # There are two successors: the final <b> tag and its text contents.
+        tag, contents = successors
+        self.assertEqual(tag['id'], '3')
+        self.assertEqual(contents, "Three")
+
+class TestPreviousOperations(ProximityTest):
+
+    def setUp(self):
+        super(TestPreviousOperations, self).setUp()
+        self.end = self.tree.find(text="Three")
+
+    def test_previous(self):
+        self.assertEqual(self.end.previous_element['id'], "3")
+        self.assertEqual(self.end.previous_element.previous_element, "Two")
+
+    def test_previous_of_first_item_is_none(self):
+        first = self.tree.find('html')
+        self.assertEqual(first.previous_element, None)
+
+    def test_previous_of_root_is_none(self):
+        # The document root is outside the next/previous chain.
+        # XXX This is broken!
+        #self.assertEqual(self.tree.previous_element, None)
+        pass
+
+    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.assertSelects(
+            self.end.find_all_previous('b'), ["Three", "Two", "One"])
+        self.assertSelects(self.end.find_all_previous(id=1), ["One"])
+
+    def test_find_previous(self):
+        self.assertEqual(self.end.find_previous('b')['id'], '3')
+        self.assertEqual(self.end.find_previous(text="One"), "One")
+
+    def test_find_previous_for_text_element(self):
+        text = self.tree.find(text="Three")
+        self.assertEqual(text.find_previous("b").string, "Three")
+        self.assertSelects(
+            text.find_all_previous("b"), ["Three", "Two", "One"])
+
+    def test_previous_generator(self):
+        start = self.tree.find(text="One")
+        predecessors = [node for node in start.previous_elements]
+
+        # There are four predecessors: the <b> tag containing "One"
+        # the <body> tag, the <head> tag, and the <html> tag.
+        b, body, head, html = predecessors
+        self.assertEqual(b['id'], '1')
+        self.assertEqual(body.name, "body")
+        self.assertEqual(head.name, "head")
+        self.assertEqual(html.name, "html")
+
+
+class SiblingTest(TreeTest):
+
+    def setUp(self):
+        super(SiblingTest, self).setUp()
+        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(self):
+        super(TestNextSibling, self).setUp()
+        self.start = self.tree.find(id="1")
+
+    def test_next_sibling_of_root_is_none(self):
+        self.assertEqual(self.tree.next_sibling, None)
+
+    def test_next_sibling(self):
+        self.assertEqual(self.start.next_sibling['id'], '2')
+        self.assertEqual(self.start.next_sibling.next_sibling['id'], '3')
+
+        # Note the difference between next_sibling and next_element.
+        self.assertEqual(self.start.next_element['id'], '1.1')
+
+    def test_next_sibling_may_not_exist(self):
+        self.assertEqual(self.tree.html.next_sibling, None)
+
+        nested_span = self.tree.find(id="1.1")
+        self.assertEqual(nested_span.next_sibling, None)
+
+        last_span = self.tree.find(id="4")
+        self.assertEqual(last_span.next_sibling, None)
+
+    def test_find_next_sibling(self):
+        self.assertEqual(self.start.find_next_sibling('span')['id'], '2')
+
+    def test_next_siblings(self):
+        self.assertSelectsIDs(self.start.find_next_siblings("span"),
+                              ['2', '3', '4'])
+
+        self.assertSelectsIDs(self.start.find_next_siblings(id='3'), ['3'])
+
+    def test_next_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(text="Foo")
+        self.assertEqual(start.next_sibling.name, 'b')
+        self.assertEqual(start.next_sibling.next_sibling, 'baz')
+
+        self.assertSelects(start.find_next_siblings('b'), ['bar'])
+        self.assertEqual(start.find_next_sibling(text="baz"), "baz")
+        self.assertEqual(start.find_next_sibling(text="nonesuch"), None)
+
+
+class TestPreviousSibling(SiblingTest):
+
+    def setUp(self):
+        super(TestPreviousSibling, self).setUp()
+        self.end = self.tree.find(id="4")
+
+    def test_previous_sibling_of_root_is_none(self):
+        self.assertEqual(self.tree.previous_sibling, None)
+
+    def test_previous_sibling(self):
+        self.assertEqual(self.end.previous_sibling['id'], '3')
+        self.assertEqual(self.end.previous_sibling.previous_sibling['id'], '2')
+
+        # Note the difference between previous_sibling and previous_element.
+        self.assertEqual(self.end.previous_element['id'], '3.1')
+
+    def test_previous_sibling_may_not_exist(self):
+        self.assertEqual(self.tree.html.previous_sibling, None)
+
+        nested_span = self.tree.find(id="1.1")
+        self.assertEqual(nested_span.previous_sibling, None)
+
+        first_span = self.tree.find(id="1")
+        self.assertEqual(first_span.previous_sibling, None)
+
+    def test_find_previous_sibling(self):
+        self.assertEqual(self.end.find_previous_sibling('span')['id'], '3')
+
+    def test_previous_siblings(self):
+        self.assertSelectsIDs(self.end.find_previous_siblings("span"),
+                              ['3', '2', '1'])
+
+        self.assertSelectsIDs(self.end.find_previous_siblings(id='1'), ['1'])
+
+    def test_previous_sibling_for_text_element(self):
+        soup = self.soup("Foo<b>bar</b>baz")
+        start = soup.find(text="baz")
+        self.assertEqual(start.previous_sibling.name, 'b')
+        self.assertEqual(start.previous_sibling.previous_sibling, 'Foo')
+
+        self.assertSelects(start.find_previous_siblings('b'), ['bar'])
+        self.assertEqual(start.find_previous_sibling(text="Foo"), "Foo")
+        self.assertEqual(start.find_previous_sibling(text="nonesuch"), None)
+
+
+class TestTag(SoupTest):
+
+    # Test various methods of Tag.
+
+    def test__should_pretty_print(self):
+        # Test the rules about when a tag should be pretty-printed.
+        tag = self.soup("").new_tag("a_tag")
+
+        # No list of whitespace-preserving tags -> pretty-print
+        tag._preserve_whitespace_tags = None
+        self.assertEqual(True, tag._should_pretty_print(0))
+
+        # List exists but tag is not on the list -> pretty-print
+        tag.preserve_whitespace_tags = ["some_other_tag"]
+        self.assertEqual(True, tag._should_pretty_print(1))
+
+        # Indent level is None -> don't pretty-print
+        self.assertEqual(False, tag._should_pretty_print(None))
+        
+        # Tag is on the whitespace-preserving list -> don't pretty-print
+        tag.preserve_whitespace_tags = ["some_other_tag", "a_tag"]
+        self.assertEqual(False, tag._should_pretty_print(1))
+
+        
+class TestTagCreation(SoupTest):
+    """Test the ability to create new tags."""
+    def test_new_tag(self):
+        soup = self.soup("")
+        new_tag = soup.new_tag("foo", bar="baz", attrs={"name": "a name"})
+        self.assertTrue(isinstance(new_tag, Tag))
+        self.assertEqual("foo", new_tag.name)
+        self.assertEqual(dict(bar="baz", name="a name"), new_tag.attrs)
+        self.assertEqual(None, new_tag.parent)
+        
+    def test_tag_inherits_self_closing_rules_from_builder(self):
+        if XML_BUILDER_PRESENT:
+            xml_soup = BeautifulSoup("", "lxml-xml")
+            xml_br = xml_soup.new_tag("br")
+            xml_p = xml_soup.new_tag("p")
+
+            # Both the <br> and <p> tag are empty-element, just because
+            # they have no contents.
+            self.assertEqual(b"<br/>", xml_br.encode())
+            self.assertEqual(b"<p/>", xml_p.encode())
+
+        html_soup = BeautifulSoup("", "html.parser")
+        html_br = html_soup.new_tag("br")
+        html_p = html_soup.new_tag("p")
+
+        # The HTML builder users HTML's rules about which tags are
+        # empty-element tags, and the new tags reflect these rules.
+        self.assertEqual(b"<br/>", html_br.encode())
+        self.assertEqual(b"<p></p>", html_p.encode())
+
+    def test_new_string_creates_navigablestring(self):
+        soup = self.soup("")
+        s = soup.new_string("foo")
+        self.assertEqual("foo", s)
+        self.assertTrue(isinstance(s, NavigableString))
+
+    def test_new_string_can_create_navigablestring_subclass(self):
+        soup = self.soup("")
+        s = soup.new_string("foo", Comment)
+        self.assertEqual("foo", s)
+        self.assertTrue(isinstance(s, Comment))
+
+class TestTreeModification(SoupTest):
+
+    def test_attribute_modification(self):
+        soup = self.soup('<a id="1"></a>')
+        soup.a['id'] = 2
+        self.assertEqual(soup.decode(), self.document_for('<a id="2"></a>'))
+        del(soup.a['id'])
+        self.assertEqual(soup.decode(), self.document_for('<a></a>'))
+        soup.a['id2'] = 'foo'
+        self.assertEqual(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)
+        self.assertEqual(
+            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.
+        self.assertEqual(bold.parent, second_para)
+
+        self.assertEqual(
+            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_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)
+        self.assertEqual(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()
+        self.assertEqual(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()
+        self.assertEqual(None, a.parent)
+        self.assertRaises(ValueError, a.unwrap)
+        self.assertRaises(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
+        soup.c.replace_with(c)
+        self.assertEqual(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)
+        self.assertRaises(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)
+        self.assertRaises(ValueError, soup.a.insert, 0, soup.a)
+
+    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)
+        soup.insert(1, to_insert)
+
+        for i in soup.descendants:
+            assert not isinstance(i, BeautifulSoup)
+        
+        p1, p2, p3, p4 = list(soup.children)
+        self.assertEqual("And now, a word:", p1.string)
+        self.assertEqual("p2", p2.string)
+        self.assertEqual("p3", p3.string)
+        self.assertEqual("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
+        b = a.contents[0]
+        # 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.replaceWith('')
+        right.replaceWith('')
+
+        # The <b> tag is still connected to the tree.
+        self.assertEqual("three", soup.b.string)
+
+    def test_replace_final_node(self):
+        soup = self.soup("<b>Argh!</b>")
+        soup.find(text="Argh!").replace_with("Hooray!")
+        new_text = soup.find(text="Hooray!")
+        b = soup.b
+        self.assertEqual(new_text.previous_element, b)
+        self.assertEqual(new_text.parent, b)
+        self.assertEqual(new_text.previous_element.next_element, new_text)
+        self.assertEqual(new_text.next_element, 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!")
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<a><b>Argh!Hooray!</b><c></c></a>"))
+
+        new_text = soup.find(text="Hooray!")
+        self.assertEqual(new_text.previous_element, "Argh!")
+        self.assertEqual(new_text.previous_element.next_element, new_text)
+
+        self.assertEqual(new_text.previous_sibling, "Argh!")
+        self.assertEqual(new_text.previous_sibling.next_sibling, new_text)
+
+        self.assertEqual(new_text.next_sibling, None)
+        self.assertEqual(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.
+        self.assertEqual(["foo", "bar"], soup.a.contents)
+        # And they were converted to NavigableStrings.
+        self.assertEqual(soup.a.contents[0].next_element, "bar")
+
+    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)
+
+        self.assertEqual(
+            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
+        self.assertEqual(b_tag.next_sibling, magic_tag)
+        self.assertEqual(magic_tag.previous_sibling, b_tag)
+
+        find = b_tag.find(text="Find")
+        self.assertEqual(find.next_element, magic_tag)
+        self.assertEqual(magic_tag.previous_element, find)
+
+        c_tag = soup.c
+        self.assertEqual(magic_tag.next_sibling, c_tag)
+        self.assertEqual(c_tag.previous_sibling, magic_tag)
+
+        the = magic_tag.find(text="the")
+        self.assertEqual(the.parent, magic_tag)
+        self.assertEqual(the.next_element, c_tag)
+        self.assertEqual(c_tag.previous_element, the)
+
+    def test_append_child_thats_already_at_the_end(self):
+        data = "<a><b></b></a>"
+        soup = self.soup(data)
+        soup.a.append(soup.b)
+        self.assertEqual(data, soup.decode())
+
+    def test_extend(self):
+        data = "<a><b><c><d><e><f><g></g></f></e></d></c></b></a>"
+        soup = self.soup(data)
+        l = [soup.g, soup.f, soup.e, soup.d, soup.c, soup.b]
+        soup.a.extend(l)
+        self.assertEqual("<a><g></g><f></f><e></e><d></d><c></c><b></b></a>", soup.decode())
+
+    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)
+        self.assertEqual("<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")
+        self.assertEqual(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")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<a>foo</a>BAZ<b>bar</b>"))
+
+        soup.a.insert_before(soup.b)
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<b>bar</b><a>foo</a>BAZ"))
+
+        # Can't insert an element before itself.
+        b = soup.b
+        self.assertRaises(ValueError, b.insert_before, b)
+
+        # Can't insert before if an element has no parent.
+        b.extract()
+        self.assertRaises(ValueError, b.insert_before, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+        
+    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")
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX BAZ<a>foo</a>BAZ QUUX<b>bar</b>"))
+
+        soup.a.insert_before(soup.b, "FOO")
+        self.assertEqual(
+            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")
+        self.assertEqual(
+            soup.decode(), self.document_for("<a>foo</a>QUUX<b>bar</b>BAZ"))
+        soup.b.insert_after(soup.a)
+        self.assertEqual(
+            soup.decode(), self.document_for("QUUX<b>bar</b><a>foo</a>BAZ"))
+
+        # Can't insert an element after itself.
+        b = soup.b
+        self.assertRaises(ValueError, b.insert_after, b)
+
+        # Can't insert after if an element has no parent.
+        b.extract()
+        self.assertRaises(ValueError, b.insert_after, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
+        
+    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")
+        self.assertEqual(
+            soup.decode(), self.document_for("<a>foo</a>QUUX BAZ<b>bar</b>BAZ QUUX"))
+        soup.b.insert_after(soup.a, "FOO ")
+        self.assertEqual(
+            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("")
+        self.assertRaises(ValueError, string.insert_after, tag)
+        self.assertRaises(NotImplementedError, soup.insert_after, tag)
+        self.assertRaises(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("")
+        self.assertRaises(ValueError, string.insert_before, tag)
+        self.assertRaises(NotImplementedError, soup.insert_before, tag)
+        self.assertRaises(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)
+        self.assertEqual(
+            soup.decode(),
+            self.document_for(
+                "<p>There's  business like <b>no</b> business</p>"))
+
+        self.assertEqual(show.parent, None)
+        self.assertEqual(no.parent, soup.p)
+        self.assertEqual(no.next_element, "no")
+        self.assertEqual(no.next_sibling, " business")
+
+    def test_replace_first_child(self):
+        data = "<a><b></b><c></c></a>"
+        soup = self.soup(data)
+        soup.b.replace_with(soup.c)
+        self.assertEqual("<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)
+        self.assertEqual("<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)
+
+        self.assertEqual(
+            soup.decode(), self.document_for(
+                "<a>We<f>refuse</f></a><e>to<g>service</g></e>"))
+
+        # The <b> tag is now an orphan.
+        self.assertEqual(remove_tag.parent, None)
+        self.assertEqual(remove_tag.find(text="right").next_element, None)
+        self.assertEqual(remove_tag.previous_element, None)
+        self.assertEqual(remove_tag.next_sibling, None)
+        self.assertEqual(remove_tag.previous_sibling, None)
+
+        # The <f> tag is now connected to the <a> tag.
+        self.assertEqual(move_tag.parent, soup.a)
+        self.assertEqual(move_tag.previous_element, "We")
+        self.assertEqual(move_tag.next_element.next_element, soup.e)
+        self.assertEqual(move_tag.next_sibling, 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(text="to")
+        g_tag = soup.g
+        self.assertEqual(to_text.next_element, g_tag)
+        self.assertEqual(to_text.next_sibling, g_tag)
+        self.assertEqual(g_tag.previous_element, to_text)
+        self.assertEqual(g_tag.previous_sibling, to_text)
+
+    def test_unwrap(self):
+        tree = self.soup("""
+            <p>Unneeded <em>formatting</em> is unneeded</p>
+            """)
+        tree.em.unwrap()
+        self.assertEqual(tree.em, None)
+        self.assertEqual(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"))
+        self.assertEqual(value.decode(), "<b>I wish I was bold.</b>")
+        self.assertEqual(
+            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)
+        self.assertEqual(
+            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)
+        self.assertEqual(2, len(soup.b.contents))
+        self.assertEqual(
+            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>')
+
+        self.assertEqual(len(soup.body.contents), 3)
+        extracted = soup.find(id="nav").extract()
+
+        self.assertEqual(
+            soup.decode(), "<html><body>Some content.  More content.</body></html>")
+        self.assertEqual(extracted.decode(), '<div id="nav">Nav crap</div>')
+
+        # The extracted tag is now an orphan.
+        self.assertEqual(len(soup.body.contents), 2)
+        self.assertEqual(extracted.parent, None)
+        self.assertEqual(extracted.previous_element, None)
+        self.assertEqual(extracted.next_element.next_element, None)
+
+        # The gap where the extracted tag used to be has been mended.
+        content_1 = soup.find(text="Some content. ")
+        content_2 = soup.find(text=" More content.")
+        self.assertEqual(content_1.next_element, content_2)
+        self.assertEqual(content_1.next_sibling, content_2)
+        self.assertEqual(content_2.previous_element, content_1)
+        self.assertEqual(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
+        bar_1 = soup.b.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()
+        self.assertEqual(foo_2, soup.a.string)
+        self.assertEqual(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")]
+        self.assertEqual("<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()
+        self.assertEqual(None, 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()
+        self.assertEqual(len(soup.p.contents), 0)
+        self.assertTrue(hasattr(a, "contents"))
+
+        # clear using decompose()
+        em = a.em
+        a.clear(decompose=True)
+        self.assertEqual(0, len(em.contents))
+
+       
+    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]:
+            self.assertEqual(False, i.decomposed)
+
+        # This sets p1 and everything beneath it to decomposed.
+        p1.decompose()
+        for i in [p1, a, text]:
+            self.assertEqual(True, i.decomposed)
+        # p2 is unaffected.
+        self.assertEqual(False, p2.decomposed)
+            
+    def test_string_set(self):
+        """Tag.string = 'string'"""
+        soup = self.soup("<a></a> <b><c></c></b>")
+        soup.a.string = "foo"
+        self.assertEqual(soup.a.contents, ["foo"])
+        soup.b.string = "bar"
+        self.assertEqual(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
+        self.assertEqual(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
+        self.assertTrue(isinstance(soup.a.string, CData))
+
+class TestElementObjects(SoupTest):
+    """Test various features of element objects."""
+
+    def test_len(self):
+        """The length of an element is its number of children."""
+        soup = self.soup("<top>1<b>2</b>3</top>")
+
+        # The BeautifulSoup object itself contains one element: the
+        # <top> tag.
+        self.assertEqual(len(soup.contents), 1)
+        self.assertEqual(len(soup), 1)
+
+        # The <top> tag contains three elements: the text node "1", the
+        # <b> tag, and the text node "3".
+        self.assertEqual(len(soup.top), 3)
+        self.assertEqual(len(soup.top.contents), 3)
+
+    def test_member_access_invokes_find(self):
+        """Accessing a Python member .foo invokes find('foo')"""
+        soup = self.soup('<b><i></i></b>')
+        self.assertEqual(soup.b, soup.find('b'))
+        self.assertEqual(soup.b.i, soup.find('b').find('i'))
+        self.assertEqual(soup.a, None)
+
+    def test_deprecated_member_access(self):
+        soup = self.soup('<b><i></i></b>')
+        with warnings.catch_warnings(record=True) as w:
+            tag = soup.bTag
+        self.assertEqual(soup.b, tag)
+        self.assertEqual(
+            '.bTag is deprecated, use .find("b") instead. If you really were looking for a tag called bTag, use .find("bTag")',
+            str(w[0].message))
+
+    def test_has_attr(self):
+        """has_attr() checks for the presence of an attribute.
+
+        Please note note: has_attr() is different from
+        __in__. has_attr() checks the tag's attributes and __in__
+        checks the tag's chidlren.
+        """
+        soup = self.soup("<foo attr='bar'>")
+        self.assertTrue(soup.foo.has_attr('attr'))
+        self.assertFalse(soup.foo.has_attr('attr2'))
+
+
+    def test_attributes_come_out_in_alphabetical_order(self):
+        markup = '<b a="1" z="5" m="3" f="2" y="4"></b>'
+        self.assertSoupEquals(markup, '<b a="1" f="2" m="3" y="4" z="5"></b>')
+
+    def test_string(self):
+        # A tag that contains only a text node makes that node
+        # available as .string.
+        soup = self.soup("<b>foo</b>")
+        self.assertEqual(soup.b.string, 'foo')
+
+    def test_empty_tag_has_no_string(self):
+        # A tag with no children has no .stirng.
+        soup = self.soup("<b></b>")
+        self.assertEqual(soup.b.string, None)
+
+    def test_tag_with_multiple_children_has_no_string(self):
+        # A tag with no children has no .string.
+        soup = self.soup("<a>foo<b></b><b></b></b>")
+        self.assertEqual(soup.b.string, None)
+
+        soup = self.soup("<a>foo<b></b>bar</b>")
+        self.assertEqual(soup.b.string, None)
+
+        # Even if all the children are strings, due to trickery,
+        # it won't work--but this would be a good optimization.
+        soup = self.soup("<a>foo</b>")
+        soup.a.insert(1, "bar")
+        self.assertEqual(soup.a.string, None)
+
+    def test_tag_with_recursive_string_has_string(self):
+        # A tag with a single child which has a .string inherits that
+        # .string.
+        soup = self.soup("<a><b>foo</b></a>")
+        self.assertEqual(soup.a.string, "foo")
+        self.assertEqual(soup.string, "foo")
+
+    def test_lack_of_string(self):
+        """Only a tag containing a single text node has a .string."""
+        soup = self.soup("<b>f<i>e</i>o</b>")
+        self.assertFalse(soup.b.string)
+
+        soup = self.soup("<b></b>")
+        self.assertFalse(soup.b.string)
+
+    def test_all_text(self):
+        """Tag.text and Tag.get_text(sep=u"") -> all child text, concatenated"""
+        soup = self.soup("<a>a<b>r</b>   <r> t </r></a>")
+        self.assertEqual(soup.a.text, "ar  t ")
+        self.assertEqual(soup.a.get_text(strip=True), "art")
+        self.assertEqual(soup.a.get_text(","), "a,r, , t ")
+        self.assertEqual(soup.a.get_text(",", strip=True), "a,r,t")
+
+    def test_get_text_ignores_special_string_containers(self):
+        soup = self.soup("foo<!--IGNORE-->bar")
+        self.assertEqual(soup.get_text(), "foobar")
+
+        self.assertEqual(
+            soup.get_text(types=(NavigableString, Comment)), "fooIGNOREbar")
+        self.assertEqual(
+            soup.get_text(types=None), "fooIGNOREbar")
+
+        soup = self.soup("foo<style>CSS</style><script>Javascript</script>bar")
+        self.assertEqual(soup.get_text(), "foobar")
+        
+    def test_all_strings_ignores_special_string_containers(self):
+        soup = self.soup("foo<!--IGNORE-->bar")
+        self.assertEqual(['foo', 'bar'], list(soup.strings))
+
+        soup = self.soup("foo<style>CSS</style><script>Javascript</script>bar")
+        self.assertEqual(['foo', 'bar'], list(soup.strings))
+
+
+class TestCDAtaListAttributes(SoupTest):
+
+    """Testing cdata-list attributes like 'class'.
+    """
+    def test_single_value_becomes_list(self):
+        soup = self.soup("<a class='foo'>")
+        self.assertEqual(["foo"],soup.a['class'])
+
+    def test_multiple_values_becomes_list(self):
+        soup = self.soup("<a class='foo bar'>")
+        self.assertEqual(["foo", "bar"], soup.a['class'])
+
+    def test_multiple_values_separated_by_weird_whitespace(self):
+        soup = self.soup("<a class='foo\tbar\nbaz'>")
+        self.assertEqual(["foo", "bar", "baz"],soup.a['class'])
+
+    def test_attributes_joined_into_string_on_output(self):
+        soup = self.soup("<a class='foo\tbar'>")
+        self.assertEqual(b'<a class="foo bar"></a>', soup.a.encode())
+
+    def test_get_attribute_list(self):
+        soup = self.soup("<a id='abc def'>")
+        self.assertEqual(['abc def'], soup.a.get_attribute_list('id'))
+        
+    def test_accept_charset(self):
+        soup = self.soup('<form accept-charset="ISO-8859-1 UTF-8">')
+        self.assertEqual(['ISO-8859-1', 'UTF-8'], soup.form['accept-charset'])
+
+    def test_cdata_attribute_applying_only_to_one_tag(self):
+        data = '<a accept-charset="ISO-8859-1 UTF-8"></a>'
+        soup = self.soup(data)
+        # We saw in another test that accept-charset is a cdata-list
+        # attribute for the <form> tag. But it's not a cdata-list
+        # attribute for any other tag.
+        self.assertEqual('ISO-8859-1 UTF-8', soup.a['accept-charset'])
+
+    def test_string_has_immutable_name_property(self):
+        string = self.soup("s").string
+        self.assertEqual(None, string.name)
+        def t():
+            string.name = 'foo'
+        self.assertRaises(AttributeError, t)
+
+class TestPersistence(SoupTest):
+    "Testing features like pickle and deepcopy."
+
+    def setUp(self):
+        super(TestPersistence, self).setUp()
+        self.page = """<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
+"http://www.w3.org/TR/REC-html40/transitional.dtd">
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+<title>Beautiful Soup: We called him Tortoise because he taught us.</title>
+<link rev="made" href="mailto:leonardr@segfault.org">
+<meta name="Description" content="Beautiful Soup: an HTML parser optimized for screen-scraping.">
+<meta name="generator" content="Markov Approximation 1.4 (module: leonardr)">
+<meta name="author" content="Leonard Richardson">
+</head>
+<body>
+<a href="foo">foo</a>
+<a href="foo"><b>bar</b></a>
+</body>
+</html>"""
+        self.tree = self.soup(self.page)
+
+    def test_pickle_and_unpickle_identity(self):
+        # Pickling a tree, then unpickling it, yields a tree identical
+        # to the original.
+        dumped = pickle.dumps(self.tree, 2)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.__class__, BeautifulSoup)
+        self.assertEqual(loaded.decode(), self.tree.decode())
+
+    def test_deepcopy_identity(self):
+        # Making a deepcopy of a tree yields an identical tree.
+        copied = copy.deepcopy(self.tree)
+        self.assertEqual(copied.decode(), self.tree.decode())
+
+    def test_copy_preserves_encoding(self):
+        soup = BeautifulSoup(b'<p>&nbsp;</p>', 'html.parser')
+        encoding = soup.original_encoding
+        copy = soup.__copy__()
+        self.assertEqual("<p> </p>", str(copy))
+        self.assertEqual(encoding, copy.original_encoding)
+
+    def test_copy_preserves_builder_information(self):
+
+        tag = self.soup('<p></p>').p
+
+        # Simulate a tag obtained from a source file.
+        tag.sourceline = 10
+        tag.sourcepos = 33
+        
+        copied = tag.__copy__()
+
+        # The TreeBuilder object is no longer availble, but information
+        # obtained from it gets copied over to the new Tag object.
+        self.assertEqual(tag.sourceline, copied.sourceline)
+        self.assertEqual(tag.sourcepos, copied.sourcepos)
+        self.assertEqual(
+            tag.can_be_empty_element, copied.can_be_empty_element
+        )
+        self.assertEqual(
+            tag.cdata_list_attributes, copied.cdata_list_attributes
+        )
+        self.assertEqual(
+            tag.preserve_whitespace_tags, copied.preserve_whitespace_tags
+        )
+        
+        
+    def test_unicode_pickle(self):
+        # A tree containing Unicode characters can be pickled.
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        dumped = pickle.dumps(soup, pickle.HIGHEST_PROTOCOL)
+        loaded = pickle.loads(dumped)
+        self.assertEqual(loaded.decode(), soup.decode())
+
+    def test_copy_navigablestring_is_not_attached_to_tree(self):
+        html = "<b>Foo<a></a></b><b>Bar</b>"
+        soup = self.soup(html)
+        s1 = soup.find(string="Foo")
+        s2 = copy.copy(s1)
+        self.assertEqual(s1, s2)
+        self.assertEqual(None, s2.parent)
+        self.assertEqual(None, s2.next_element)
+        self.assertNotEqual(None, s1.next_sibling)
+        self.assertEqual(None, s2.next_sibling)
+        self.assertEqual(None, s2.previous_element)
+
+    def test_copy_navigablestring_subclass_has_same_type(self):
+        html = "<b><!--Foo--></b>"
+        soup = self.soup(html)
+        s1 = soup.string
+        s2 = copy.copy(s1)
+        self.assertEqual(s1, s2)
+        self.assertTrue(isinstance(s2, Comment))
+
+    def test_copy_entire_soup(self):
+        html = "<div><b>Foo<a></a></b><b>Bar</b></div>end"
+        soup = self.soup(html)
+        soup_copy = copy.copy(soup)
+        self.assertEqual(soup, soup_copy)
+
+    def test_copy_tag_copies_contents(self):
+        html = "<div><b>Foo<a></a></b><b>Bar</b></div>end"
+        soup = self.soup(html)
+        div = soup.div
+        div_copy = copy.copy(div)
+
+        # The two tags look the same, and evaluate to equal.
+        self.assertEqual(str(div), str(div_copy))
+        self.assertEqual(div, div_copy)
+
+        # But they're not the same object.
+        self.assertFalse(div is div_copy)
+
+        # And they don't have the same relation to the parse tree. The
+        # copy is not associated with a parse tree at all.
+        self.assertEqual(None, div_copy.parent)
+        self.assertEqual(None, div_copy.previous_element)
+        self.assertEqual(None, div_copy.find(string='Bar').next_element)
+        self.assertNotEqual(None, div.find(string='Bar').next_element)
+
+class TestSubstitutions(SoupTest):
+
+    def test_default_formatter_is_minimal(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="minimal")
+        # The < is converted back into &lt; but the e-with-acute is left alone.
+        self.assertEqual(
+            decoded,
+            self.document_for(
+                "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"))
+
+    def test_formatter_html(self):
+        markup = "<br><b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="html")
+        self.assertEqual(
+            decoded,
+            self.document_for("<br/><b>&lt;&lt;Sacr&eacute; bleu!&gt;&gt;</b>"))
+
+    def test_formatter_html5(self):
+        markup = "<br><b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="html5")
+        self.assertEqual(
+            decoded,
+            self.document_for("<br><b>&lt;&lt;Sacr&eacute; bleu!&gt;&gt;</b>"))
+        
+    def test_formatter_minimal(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter="minimal")
+        # The < is converted back into &lt; but the e-with-acute is left alone.
+        self.assertEqual(
+            decoded,
+            self.document_for(
+                "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"))
+
+    def test_formatter_null(self):
+        markup = "<b>&lt;&lt;Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!&gt;&gt;</b>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter=None)
+        # Neither the angle brackets nor the e-with-acute are converted.
+        # This is not valid HTML, but it's what the user wanted.
+        self.assertEqual(decoded,
+                          self.document_for("<b><<Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!>></b>"))
+
+    def test_formatter_custom(self):
+        markup = "<b>&lt;foo&gt;</b><b>bar</b><br/>"
+        soup = self.soup(markup)
+        decoded = soup.decode(formatter = lambda x: x.upper())
+        # Instead of normal entity conversion code, the custom
+        # callable is called on every string.
+        self.assertEqual(
+            decoded,
+            self.document_for("<b><FOO></b><b>BAR</b><br/>"))
+
+    def test_formatter_is_run_on_attribute_values(self):
+        markup = '<a href="http://a.com?a=b&c=é">e</a>'
+        soup = self.soup(markup)
+        a = soup.a
+
+        expect_minimal = '<a href="http://a.com?a=b&amp;c=é">e</a>'
+
+        self.assertEqual(expect_minimal, a.decode())
+        self.assertEqual(expect_minimal, a.decode(formatter="minimal"))
+
+        expect_html = '<a href="http://a.com?a=b&amp;c=&eacute;">e</a>'
+        self.assertEqual(expect_html, a.decode(formatter="html"))
+
+        self.assertEqual(markup, a.decode(formatter=None))
+        expect_upper = '<a href="HTTP://A.COM?A=B&C=É">E</a>'
+        self.assertEqual(expect_upper, a.decode(formatter=lambda x: x.upper()))
+
+    def test_formatter_skips_script_tag_for_html_documents(self):
+        doc = """
+  <script type="text/javascript">
+   console.log("< < hey > > ");
+  </script>
+"""
+        encoded = BeautifulSoup(doc, 'html.parser').encode()
+        self.assertTrue(b"< < hey > >" in encoded)
+
+    def test_formatter_skips_style_tag_for_html_documents(self):
+        doc = """
+  <style type="text/css">
+   console.log("< < hey > > ");
+  </style>
+"""
+        encoded = BeautifulSoup(doc, 'html.parser').encode()
+        self.assertTrue(b"< < hey > >" in encoded)
+
+    def test_prettify_leaves_preformatted_text_alone(self):
+        soup = self.soup("<div>  foo  <pre>  \tbar\n  \n  </pre>  baz  <textarea> eee\nfff\t</textarea></div>")
+        # Everything outside the <pre> tag is reformatted, but everything
+        # inside is left alone.
+        self.assertEqual(
+            '<div>\n foo\n <pre>  \tbar\n  \n  </pre>\n baz\n <textarea> eee\nfff\t</textarea>\n</div>',
+            soup.div.prettify())
+
+    def test_prettify_accepts_formatter_function(self):
+        soup = BeautifulSoup("<html><body>foo</body></html>", 'html.parser')
+        pretty = soup.prettify(formatter = lambda x: x.upper())
+        self.assertTrue("FOO" in pretty)
+
+    def test_prettify_outputs_unicode_by_default(self):
+        soup = self.soup("<a></a>")
+        self.assertEqual(str, type(soup.prettify()))
+
+    def test_prettify_can_encode_data(self):
+        soup = self.soup("<a></a>")
+        self.assertEqual(bytes, type(soup.prettify("utf-8")))
+
+    def test_html_entity_substitution_off_by_default(self):
+        markup = "<b>Sacr\N{LATIN SMALL LETTER E WITH ACUTE} bleu!</b>"
+        soup = self.soup(markup)
+        encoded = soup.b.encode("utf-8")
+        self.assertEqual(encoded, markup.encode('utf-8'))
+
+    def test_encoding_substitution(self):
+        # Here's the <meta> tag saying that a document is
+        # encoded in Shift-JIS.
+        meta_tag = ('<meta content="text/html; charset=x-sjis" '
+                    'http-equiv="Content-type"/>')
+        soup = self.soup(meta_tag)
+
+        # Parse the document, and the charset apprears unchanged.
+        self.assertEqual(soup.meta['content'], 'text/html; charset=x-sjis')
+
+        # Encode the document into some encoding, and the encoding is
+        # substituted into the meta tag.
+        utf_8 = soup.encode("utf-8")
+        self.assertTrue(b"charset=utf-8" in utf_8)
+
+        euc_jp = soup.encode("euc_jp")
+        self.assertTrue(b"charset=euc_jp" in euc_jp)
+
+        shift_jis = soup.encode("shift-jis")
+        self.assertTrue(b"charset=shift-jis" in shift_jis)
+
+        utf_16_u = soup.encode("utf-16").decode("utf-16")
+        self.assertTrue("charset=utf-16" in utf_16_u)
+
+    def test_encoding_substitution_doesnt_happen_if_tag_is_strained(self):
+        markup = ('<head><meta content="text/html; charset=x-sjis" '
+                    'http-equiv="Content-type"/></head><pre>foo</pre>')
+
+        # Beautiful Soup used to try to rewrite the meta tag even if the
+        # meta tag got filtered out by the strainer. This test makes
+        # sure that doesn't happen.
+        strainer = SoupStrainer('pre')
+        soup = self.soup(markup, parse_only=strainer)
+        self.assertEqual(soup.contents[0].name, 'pre')
+
+class TestEncoding(SoupTest):
+    """Test the ability to encode objects into strings."""
+
+    def test_unicode_string_can_be_encoded(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(soup.b.string.encode("utf-8"),
+                          "\N{SNOWMAN}".encode("utf-8"))
+
+    def test_tag_containing_unicode_string_can_be_encoded(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            soup.b.encode("utf-8"), html.encode("utf-8"))
+
+    def test_encoding_substitutes_unrecognized_characters_by_default(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(soup.b.encode("ascii"), b"<b>&#9731;</b>")
+
+    def test_encoding_can_be_made_strict(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertRaises(
+            UnicodeEncodeError, soup.encode, "ascii", errors="strict")
+
+    def test_decode_contents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual("\N{SNOWMAN}", soup.b.decode_contents())
+
+    def test_encode_contents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            "\N{SNOWMAN}".encode("utf8"), soup.b.encode_contents(
+                encoding="utf8"))
+
+    def test_deprecated_renderContents(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        self.assertEqual(
+            "\N{SNOWMAN}".encode("utf8"), soup.b.renderContents())
+
+    def test_repr(self):
+        html = "<b>\N{SNOWMAN}</b>"
+        soup = self.soup(html)
+        if PY3K:
+            self.assertEqual(html, repr(soup))
+        else:
+            self.assertEqual(b'<b>\\u2603</b>', repr(soup))
+
+class TestFormatter(SoupTest):
+
+    def test_default_attributes(self):
+        # Test the default behavior of Formatter.attributes().
+        formatter = Formatter()
+        tag = Tag(name="tag")
+        tag['b'] = 1
+        tag['a'] = 2
+
+        # Attributes come out sorted by name. In Python 3, attributes
+        # normally come out of a dictionary in the order they were
+        # added.
+        self.assertEqual([('a', 2), ('b', 1)], formatter.attributes(tag))
+
+        # This works even if Tag.attrs is None, though this shouldn't
+        # normally happen.
+        tag.attrs = None
+        self.assertEqual([], formatter.attributes(tag))
+        
+    def test_sort_attributes(self):
+        # Test the ability to override Formatter.attributes() to,
+        # e.g., disable the normal sorting of attributes.
+        class UnsortedFormatter(Formatter):
+            def attributes(self, tag):
+                self.called_with = tag
+                for k, v in sorted(tag.attrs.items()):
+                    if k == 'ignore':
+                        continue
+                    yield k,v
+
+        soup = self.soup('<p cval="1" aval="2" ignore="ignored"></p>')
+        formatter = UnsortedFormatter()
+        decoded = soup.decode(formatter=formatter)
+
+        # attributes() was called on the <p> tag. It filtered out one
+        # attribute and sorted the other two.
+        self.assertEqual(formatter.called_with, soup.p)
+        self.assertEqual('<p aval="2" cval="1"></p>', decoded)
+
+
+class TestNavigableStringSubclasses(SoupTest):
+
+    def test_cdata(self):
+        # None of the current builders turn CDATA sections into CData
+        # objects, but you can create them manually.
+        soup = self.soup("")
+        cdata = CData("foo")
+        soup.insert(1, cdata)
+        self.assertEqual(str(soup), "<![CDATA[foo]]>")
+        self.assertEqual(soup.find(text="foo"), "foo")
+        self.assertEqual(soup.contents[0], "foo")
+
+    def test_cdata_is_never_formatted(self):
+        """Text inside a CData object is passed into the formatter.
+
+        But the return value is ignored.
+        """
+
+        self.count = 0
+        def increment(*args):
+            self.count += 1
+            return "BITTER FAILURE"
+
+        soup = self.soup("")
+        cdata = CData("<><><>")
+        soup.insert(1, cdata)
+        self.assertEqual(
+            b"<![CDATA[<><><>]]>", soup.encode(formatter=increment))
+        self.assertEqual(1, self.count)
+
+    def test_doctype_ends_in_newline(self):
+        # Unlike other NavigableString subclasses, a DOCTYPE always ends
+        # in a newline.
+        doctype = Doctype("foo")
+        soup = self.soup("")
+        soup.insert(1, doctype)
+        self.assertEqual(soup.encode(), b"<!DOCTYPE foo>\n")
+
+    def test_declaration(self):
+        d = Declaration("foo")
+        self.assertEqual("<?foo?>", d.output_ready())
+
+    def test_default_string_containers(self):
+        # In some cases, we use different NavigableString subclasses for
+        # the same text in different tags.
+        soup = self.soup(
+            "<div>text</div><script>text</script><style>text</style>"
+        )
+        self.assertEqual(
+            [NavigableString, Script, Stylesheet],
+            [x.__class__ for x in soup.find_all(text=True)]
+        )
+
+        # The TemplateString is a little unusual because it's generally found
+        # _inside_ children of a <template> element, not a direct child of the
+        # <template> element.
+        soup = self.soup(
+            "<template>Some text<p>In a tag</p></template>Some text outside"
+        )
+        assert all(isinstance(x, TemplateString) for x in soup.template.strings)
+
+        # Once the <template> tag closed, we went back to using
+        # NavigableString.
+        outside = soup.template.next_sibling
+        assert isinstance(outside, NavigableString)
+        assert not isinstance(outside, TemplateString)
+
+class TestSoupSelector(TreeTest):
+
+    HTML = """
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+"http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<title>The title</title>
+<link rel="stylesheet" href="blah.css" type="text/css" id="l1">
+</head>
+<body>
+<custom-dashed-tag class="dashed" id="dash1">Hello there.</custom-dashed-tag>
+<div id="main" class="fancy">
+<div id="inner">
+<h1 id="header1">An H1</h1>
+<p>Some text</p>
+<p class="onep" id="p1">Some more text</p>
+<h2 id="header2">An H2</h2>
+<p class="class1 class2 class3" id="pmulti">Another</p>
+<a href="http://bob.example.org/" rel="friend met" id="bob">Bob</a>
+<h2 id="header3">Another H2</h2>
+<a id="me" href="http://simonwillison.net/" rel="me">me</a>
+<span class="s1">
+<a href="#" id="s1a1">span1a1</a>
+<a href="#" id="s1a2">span1a2 <span id="s1a2s1">test</span></a>
+<span class="span2">
+<a href="#" id="s2a1">span2a1</a>
+</span>
+<span class="span3"></span>
+<custom-dashed-tag class="dashed" id="dash2"/>
+<div data-tag="dashedvalue" id="data1"/>
+</span>
+</div>
+<x id="xid">
+<z id="zida"/>
+<z id="zidab"/>
+<z id="zidac"/>
+</x>
+<y id="yid">
+<z id="zidb"/>
+</y>
+<p lang="en" id="lang-en">English</p>
+<p lang="en-gb" id="lang-en-gb">English UK</p>
+<p lang="en-us" id="lang-en-us">English US</p>
+<p lang="fr" id="lang-fr">French</p>
+</div>
+
+<div id="footer">
+</div>
+"""
+
+    def setUp(self):
+        self.soup = BeautifulSoup(self.HTML, 'html.parser')
+
+    def assertSelects(self, selector, expected_ids, **kwargs):
+        el_ids = [el['id'] for el in self.soup.select(selector, **kwargs)]
+        el_ids.sort()
+        expected_ids.sort()
+        self.assertEqual(expected_ids, el_ids,
+            "Selector %s, expected [%s], got [%s]" % (
+                selector, ', '.join(expected_ids), ', '.join(el_ids)
+            )
+        )
+
+    assertSelect = assertSelects
+
+    def assertSelectMultiple(self, *tests):
+        for selector, expected_ids in tests:
+            self.assertSelect(selector, expected_ids)
+
+    def test_one_tag_one(self):
+        els = self.soup.select('title')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].name, 'title')
+        self.assertEqual(els[0].contents, ['The title'])
+
+    def test_one_tag_many(self):
+        els = self.soup.select('div')
+        self.assertEqual(len(els), 4)
+        for div in els:
+            self.assertEqual(div.name, 'div')
+
+        el = self.soup.select_one('div')
+        self.assertEqual('main', el['id'])
+
+    def test_select_one_returns_none_if_no_match(self):
+        match = self.soup.select_one('nonexistenttag')
+        self.assertEqual(None, match)
+
+
+    def test_tag_in_tag_one(self):
+        els = self.soup.select('div div')
+        self.assertSelects('div div', ['inner', 'data1'])
+
+    def test_tag_in_tag_many(self):
+        for selector in ('html div', 'html body div', 'body div'):
+            self.assertSelects(selector, ['data1', 'main', 'inner', 'footer'])
+
+
+    def test_limit(self):
+        self.assertSelects('html div', ['main'], limit=1)
+        self.assertSelects('html body div', ['inner', 'main'], limit=2)
+        self.assertSelects('body div', ['data1', 'main', 'inner', 'footer'],
+                           limit=10)
+
+    def test_tag_no_match(self):
+        self.assertEqual(len(self.soup.select('del')), 0)
+
+    def test_invalid_tag(self):
+        self.assertRaises(SyntaxError, self.soup.select, 'tag%t')
+
+    def test_select_dashed_tag_ids(self):
+        self.assertSelects('custom-dashed-tag', ['dash1', 'dash2'])
+
+    def test_select_dashed_by_id(self):
+        dashed = self.soup.select('custom-dashed-tag[id=\"dash2\"]')
+        self.assertEqual(dashed[0].name, 'custom-dashed-tag')
+        self.assertEqual(dashed[0]['id'], 'dash2')
+
+    def test_dashed_tag_text(self):
+        self.assertEqual(self.soup.select('body > custom-dashed-tag')[0].text, 'Hello there.')
+
+    def test_select_dashed_matches_find_all(self):
+        self.assertEqual(self.soup.select('custom-dashed-tag'), self.soup.find_all('custom-dashed-tag'))
+
+    def test_header_tags(self):
+        self.assertSelectMultiple(
+            ('h1', ['header1']),
+            ('h2', ['header2', 'header3']),
+        )
+
+    def test_class_one(self):
+        for selector in ('.onep', 'p.onep', 'html p.onep'):
+            els = self.soup.select(selector)
+            self.assertEqual(len(els), 1)
+            self.assertEqual(els[0].name, 'p')
+            self.assertEqual(els[0]['class'], ['onep'])
+
+    def test_class_mismatched_tag(self):
+        els = self.soup.select('div.onep')
+        self.assertEqual(len(els), 0)
+
+    def test_one_id(self):
+        for selector in ('div#inner', '#inner', 'div div#inner'):
+            self.assertSelects(selector, ['inner'])
+
+    def test_bad_id(self):
+        els = self.soup.select('#doesnotexist')
+        self.assertEqual(len(els), 0)
+
+    def test_items_in_id(self):
+        els = self.soup.select('div#inner p')
+        self.assertEqual(len(els), 3)
+        for el in els:
+            self.assertEqual(el.name, 'p')
+        self.assertEqual(els[1]['class'], ['onep'])
+        self.assertFalse(els[0].has_attr('class'))
+
+    def test_a_bunch_of_emptys(self):
+        for selector in ('div#main del', 'div#main div.oops', 'div div#main'):
+            self.assertEqual(len(self.soup.select(selector)), 0)
+
+    def test_multi_class_support(self):
+        for selector in ('.class1', 'p.class1', '.class2', 'p.class2',
+            '.class3', 'p.class3', 'html p.class2', 'div#inner .class2'):
+            self.assertSelects(selector, ['pmulti'])
+
+    def test_multi_class_selection(self):
+        for selector in ('.class1.class3', '.class3.class2',
+                         '.class1.class2.class3'):
+            self.assertSelects(selector, ['pmulti'])
+
+    def test_child_selector(self):
+        self.assertSelects('.s1 > a', ['s1a1', 's1a2'])
+        self.assertSelects('.s1 > a span', ['s1a2s1'])
+
+    def test_child_selector_id(self):
+        self.assertSelects('.s1 > a#s1a2 span', ['s1a2s1'])
+
+    def test_attribute_equals(self):
+        self.assertSelectMultiple(
+            ('p[class="onep"]', ['p1']),
+            ('p[id="p1"]', ['p1']),
+            ('[class="onep"]', ['p1']),
+            ('[id="p1"]', ['p1']),
+            ('link[rel="stylesheet"]', ['l1']),
+            ('link[type="text/css"]', ['l1']),
+            ('link[href="blah.css"]', ['l1']),
+            ('link[href="no-blah.css"]', []),
+            ('[rel="stylesheet"]', ['l1']),
+            ('[type="text/css"]', ['l1']),
+            ('[href="blah.css"]', ['l1']),
+            ('[href="no-blah.css"]', []),
+            ('p[href="no-blah.css"]', []),
+            ('[href="no-blah.css"]', []),
+        )
+
+    def test_attribute_tilde(self):
+        self.assertSelectMultiple(
+            ('p[class~="class1"]', ['pmulti']),
+            ('p[class~="class2"]', ['pmulti']),
+            ('p[class~="class3"]', ['pmulti']),
+            ('[class~="class1"]', ['pmulti']),
+            ('[class~="class2"]', ['pmulti']),
+            ('[class~="class3"]', ['pmulti']),
+            ('a[rel~="friend"]', ['bob']),
+            ('a[rel~="met"]', ['bob']),
+            ('[rel~="friend"]', ['bob']),
+            ('[rel~="met"]', ['bob']),
+        )
+
+    def test_attribute_startswith(self):
+        self.assertSelectMultiple(
+            ('[rel^="style"]', ['l1']),
+            ('link[rel^="style"]', ['l1']),
+            ('notlink[rel^="notstyle"]', []),
+            ('[rel^="notstyle"]', []),
+            ('link[rel^="notstyle"]', []),
+            ('link[href^="bla"]', ['l1']),
+            ('a[href^="http://"]', ['bob', 'me']),
+            ('[href^="http://"]', ['bob', 'me']),
+            ('[id^="p"]', ['pmulti', 'p1']),
+            ('[id^="m"]', ['me', 'main']),
+            ('div[id^="m"]', ['main']),
+            ('a[id^="m"]', ['me']),
+            ('div[data-tag^="dashed"]', ['data1'])
+        )
+
+    def test_attribute_endswith(self):
+        self.assertSelectMultiple(
+            ('[href$=".css"]', ['l1']),
+            ('link[href$=".css"]', ['l1']),
+            ('link[id$="1"]', ['l1']),
+            ('[id$="1"]', ['data1', 'l1', 'p1', 'header1', 's1a1', 's2a1', 's1a2s1', 'dash1']),
+            ('div[id$="1"]', ['data1']),
+            ('[id$="noending"]', []),
+        )
+
+    def test_attribute_contains(self):
+        self.assertSelectMultiple(
+            # From test_attribute_startswith
+            ('[rel*="style"]', ['l1']),
+            ('link[rel*="style"]', ['l1']),
+            ('notlink[rel*="notstyle"]', []),
+            ('[rel*="notstyle"]', []),
+            ('link[rel*="notstyle"]', []),
+            ('link[href*="bla"]', ['l1']),
+            ('[href*="http://"]', ['bob', 'me']),
+            ('[id*="p"]', ['pmulti', 'p1']),
+            ('div[id*="m"]', ['main']),
+            ('a[id*="m"]', ['me']),
+            # From test_attribute_endswith
+            ('[href*=".css"]', ['l1']),
+            ('link[href*=".css"]', ['l1']),
+            ('link[id*="1"]', ['l1']),
+            ('[id*="1"]', ['data1', 'l1', 'p1', 'header1', 's1a1', 's1a2', 's2a1', 's1a2s1', 'dash1']),
+            ('div[id*="1"]', ['data1']),
+            ('[id*="noending"]', []),
+            # New for this test
+            ('[href*="."]', ['bob', 'me', 'l1']),
+            ('a[href*="."]', ['bob', 'me']),
+            ('link[href*="."]', ['l1']),
+            ('div[id*="n"]', ['main', 'inner']),
+            ('div[id*="nn"]', ['inner']),
+            ('div[data-tag*="edval"]', ['data1'])
+        )
+
+    def test_attribute_exact_or_hypen(self):
+        self.assertSelectMultiple(
+            ('p[lang|="en"]', ['lang-en', 'lang-en-gb', 'lang-en-us']),
+            ('[lang|="en"]', ['lang-en', 'lang-en-gb', 'lang-en-us']),
+            ('p[lang|="fr"]', ['lang-fr']),
+            ('p[lang|="gb"]', []),
+        )
+
+    def test_attribute_exists(self):
+        self.assertSelectMultiple(
+            ('[rel]', ['l1', 'bob', 'me']),
+            ('link[rel]', ['l1']),
+            ('a[rel]', ['bob', 'me']),
+            ('[lang]', ['lang-en', 'lang-en-gb', 'lang-en-us', 'lang-fr']),
+            ('p[class]', ['p1', 'pmulti']),
+            ('[blah]', []),
+            ('p[blah]', []),
+            ('div[data-tag]', ['data1'])
+        )
+
+    def test_quoted_space_in_selector_name(self):
+        html = """<div style="display: wrong">nope</div>
+        <div style="display: right">yes</div>
+        """
+        soup = BeautifulSoup(html, 'html.parser')
+        [chosen] = soup.select('div[style="display: right"]')
+        self.assertEqual("yes", chosen.string)
+
+    def test_unsupported_pseudoclass(self):
+        self.assertRaises(
+            NotImplementedError, self.soup.select, "a:no-such-pseudoclass")
+
+        self.assertRaises(
+            SyntaxError, self.soup.select, "a:nth-of-type(a)")
+
+    def test_nth_of_type(self):
+        # Try to select first paragraph
+        els = self.soup.select('div#inner p:nth-of-type(1)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Some text')
+
+        # Try to select third paragraph
+        els = self.soup.select('div#inner p:nth-of-type(3)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Another')
+
+        # Try to select (non-existent!) fourth paragraph
+        els = self.soup.select('div#inner p:nth-of-type(4)')
+        self.assertEqual(len(els), 0)
+
+        # Zero will select no tags.
+        els = self.soup.select('div p:nth-of-type(0)')
+        self.assertEqual(len(els), 0)
+
+    def test_nth_of_type_direct_descendant(self):
+        els = self.soup.select('div#inner > p:nth-of-type(1)')
+        self.assertEqual(len(els), 1)
+        self.assertEqual(els[0].string, 'Some text')
+
+    def test_id_child_selector_nth_of_type(self):
+        self.assertSelects('#inner > p:nth-of-type(2)', ['p1'])
+
+    def test_select_on_element(self):
+        # Other tests operate on the tree; this operates on an element
+        # within the tree.
+        inner = self.soup.find("div", id="main")
+        selected = inner.select("div")
+        # The <div id="inner"> tag was selected. The <div id="footer">
+        # tag was not.
+        self.assertSelectsIDs(selected, ['inner', 'data1'])
+
+    def test_overspecified_child_id(self):
+        self.assertSelects(".fancy #inner", ['inner'])
+        self.assertSelects(".normal #inner", [])
+
+    def test_adjacent_sibling_selector(self):
+        self.assertSelects('#p1 + h2', ['header2'])
+        self.assertSelects('#p1 + h2 + p', ['pmulti'])
+        self.assertSelects('#p1 + #header2 + .class1', ['pmulti'])
+        self.assertEqual([], self.soup.select('#p1 + p'))
+
+    def test_general_sibling_selector(self):
+        self.assertSelects('#p1 ~ h2', ['header2', 'header3'])
+        self.assertSelects('#p1 ~ #header2', ['header2'])
+        self.assertSelects('#p1 ~ h2 + a', ['me'])
+        self.assertSelects('#p1 ~ h2 + [rel="me"]', ['me'])
+        self.assertEqual([], self.soup.select('#inner ~ h2'))
+
+    def test_dangling_combinator(self):
+        self.assertRaises(SyntaxError, self.soup.select, 'h1 >')
+
+    def test_sibling_combinator_wont_select_same_tag_twice(self):
+        self.assertSelects('p[lang] ~ p', ['lang-en-gb', 'lang-en-us', 'lang-fr'])
+
+    # Test the selector grouping operator (the comma)
+    def test_multiple_select(self):
+        self.assertSelects('x, y', ['xid', 'yid'])
+
+    def test_multiple_select_with_no_space(self):
+        self.assertSelects('x,y', ['xid', 'yid'])
+
+    def test_multiple_select_with_more_space(self):
+        self.assertSelects('x,    y', ['xid', 'yid'])
+
+    def test_multiple_select_duplicated(self):
+        self.assertSelects('x, x', ['xid'])
+
+    def test_multiple_select_sibling(self):
+        self.assertSelects('x, y ~ p[lang=fr]', ['xid', 'lang-fr'])
+
+    def test_multiple_select_tag_and_direct_descendant(self):
+        self.assertSelects('x, y > z', ['xid', 'zidb'])
+
+    def test_multiple_select_direct_descendant_and_tags(self):
+        self.assertSelects('div > x, y, z', ['xid', 'yid', 'zida', 'zidb', 'zidab', 'zidac'])
+
+    def test_multiple_select_indirect_descendant(self):
+        self.assertSelects('div x,y,  z', ['xid', 'yid', 'zida', 'zidb', 'zidab', 'zidac'])
+
+    def test_invalid_multiple_select(self):
+        self.assertRaises(SyntaxError, self.soup.select, ',x, y')
+        self.assertRaises(SyntaxError, self.soup.select, 'x,,y')
+
+    def test_multiple_select_attrs(self):
+        self.assertSelects('p[lang=en], p[lang=en-gb]', ['lang-en', 'lang-en-gb'])
+
+    def test_multiple_select_ids(self):
+        self.assertSelects('x, y > z[id=zida], z[id=zidab], z[id=zidb]', ['xid', 'zidb', 'zidab'])
+
+    def test_multiple_select_nested(self):
+        self.assertSelects('body > div > x, y > z', ['xid', 'zidb'])
+
+    def test_select_duplicate_elements(self):
+        # When markup contains duplicate elements, a multiple select
+        # will find all of them.
+        markup = '<div class="c1"/><div class="c2"/><div class="c1"/>'
+        soup = BeautifulSoup(markup, 'html.parser')
+        selected = soup.select(".c1, .c2")
+        self.assertEqual(3, len(selected))
+
+        # Verify that find_all finds the same elements, though because
+        # of an implementation detail it finds them in a different
+        # order.
+        for element in soup.find_all(class_=['c1', 'c2']):
+            assert element in selected