diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
new file mode 100644
index 000000000..fb0d409da
--- /dev/null
+++ b/Lib/test/test_collections.py
@@ -0,0 +1,2227 @@
+"""Unit tests for collections.py."""
+
+import collections
+import copy
+import doctest
+import inspect
+import operator
+import pickle
+from random import choice, randrange
+import string
+import sys
+from test import support
+import types
+import unittest
+
+from collections import namedtuple, Counter, OrderedDict, _count_elements
+from collections import UserDict, UserString, UserList
+from collections import ChainMap
+from collections import deque
+from collections.abc import Awaitable, Coroutine
+from collections.abc import AsyncIterator, AsyncIterable, AsyncGenerator
+from collections.abc import Hashable, Iterable, Iterator, Generator, Reversible
+from collections.abc import Sized, Container, Callable, Collection
+from collections.abc import Set, MutableSet
+from collections.abc import Mapping, MutableMapping, KeysView, ItemsView, ValuesView
+from collections.abc import Sequence, MutableSequence
+from collections.abc import ByteString
+
+
+class TestUserObjects(unittest.TestCase):
+    def _superset_test(self, a, b):
+        self.assertGreaterEqual(
+            set(dir(a)),
+            set(dir(b)),
+            '{a} should have all the methods of {b}'.format(
+                a=a.__name__,
+                b=b.__name__,
+            ),
+        )
+
+    def _copy_test(self, obj):
+        # Test internal copy
+        obj_copy = obj.copy()
+        self.assertIsNot(obj.data, obj_copy.data)
+        self.assertEqual(obj.data, obj_copy.data)
+
+        # Test copy.copy
+        obj.test = [1234]  # Make sure instance vars are also copied.
+        obj_copy = copy.copy(obj)
+        self.assertIsNot(obj.data, obj_copy.data)
+        self.assertEqual(obj.data, obj_copy.data)
+        self.assertIs(obj.test, obj_copy.test)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_str_protocol(self):
+        self._superset_test(UserString, str)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_list_protocol(self):
+        self._superset_test(UserList, list)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_dict_protocol(self):
+        self._superset_test(UserDict, dict)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_list_copy(self):
+        obj = UserList()
+        obj.append(123)
+        self._copy_test(obj)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_dict_copy(self):
+        obj = UserDict()
+        obj[123] = "abc"
+        self._copy_test(obj)
+
+
+################################################################################
+### ChainMap (helper class for configparser and the string module)
+################################################################################
+
+class TestChainMap(unittest.TestCase):
+
+    def test_basics(self):
+        c = ChainMap()
+        c['a'] = 1
+        c['b'] = 2
+        d = c.new_child()
+        d['b'] = 20
+        d['c'] = 30
+        self.assertEqual(d.maps, [{'b':20, 'c':30}, {'a':1, 'b':2}])  # check internal state
+        self.assertEqual(d.items(), dict(a=1, b=20, c=30).items())    # check items/iter/getitem
+        self.assertEqual(len(d), 3)                                   # check len
+        for key in 'abc':                                             # check contains
+            self.assertIn(key, d)
+        for k, v in dict(a=1, b=20, c=30, z=100).items():             # check get
+            self.assertEqual(d.get(k, 100), v)
+
+        del d['b']                                                    # unmask a value
+        self.assertEqual(d.maps, [{'c':30}, {'a':1, 'b':2}])          # check internal state
+        self.assertEqual(d.items(), dict(a=1, b=2, c=30).items())     # check items/iter/getitem
+        self.assertEqual(len(d), 3)                                   # check len
+        for key in 'abc':                                             # check contains
+            self.assertIn(key, d)
+        for k, v in dict(a=1, b=2, c=30, z=100).items():              # check get
+            self.assertEqual(d.get(k, 100), v)
+        self.assertIn(repr(d), [                                      # check repr
+            type(d).__name__ + "({'c': 30}, {'a': 1, 'b': 2})",
+            type(d).__name__ + "({'c': 30}, {'b': 2, 'a': 1})"
+        ])
+
+        for e in d.copy(), copy.copy(d):                               # check shallow copies
+            self.assertEqual(d, e)
+            self.assertEqual(d.maps, e.maps)
+            self.assertIsNot(d, e)
+            self.assertIsNot(d.maps[0], e.maps[0])
+            for m1, m2 in zip(d.maps[1:], e.maps[1:]):
+                self.assertIs(m1, m2)
+
+        # check deep copies
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            e = pickle.loads(pickle.dumps(d, proto))
+            self.assertEqual(d, e)
+            self.assertEqual(d.maps, e.maps)
+            self.assertIsNot(d, e)
+            for m1, m2 in zip(d.maps, e.maps):
+                self.assertIsNot(m1, m2, e)
+        for e in [copy.deepcopy(d),
+                  eval(repr(d))
+                ]:
+            self.assertEqual(d, e)
+            self.assertEqual(d.maps, e.maps)
+            self.assertIsNot(d, e)
+            for m1, m2 in zip(d.maps, e.maps):
+                self.assertIsNot(m1, m2, e)
+
+        f = d.new_child()
+        f['b'] = 5
+        self.assertEqual(f.maps, [{'b': 5}, {'c':30}, {'a':1, 'b':2}])
+        self.assertEqual(f.parents.maps, [{'c':30}, {'a':1, 'b':2}])   # check parents
+        self.assertEqual(f['b'], 5)                                    # find first in chain
+        self.assertEqual(f.parents['b'], 2)                            # look beyond maps[0]
+
+    def test_ordering(self):
+        # Combined order matches a series of dict updates from last to first.
+        # This test relies on the ordering of the underlying dicts.
+
+        baseline = {'music': 'bach', 'art': 'rembrandt'}
+        adjustments = {'art': 'van gogh', 'opera': 'carmen'}
+
+        cm = ChainMap(adjustments, baseline)
+
+        combined = baseline.copy()
+        combined.update(adjustments)
+
+        self.assertEqual(list(combined.items()), list(cm.items()))
+
+    def test_constructor(self):
+        self.assertEqual(ChainMap().maps, [{}])                        # no-args --> one new dict
+        self.assertEqual(ChainMap({1:2}).maps, [{1:2}])                # 1 arg --> list
+
+    def test_bool(self):
+        self.assertFalse(ChainMap())
+        self.assertFalse(ChainMap({}, {}))
+        self.assertTrue(ChainMap({1:2}, {}))
+        self.assertTrue(ChainMap({}, {1:2}))
+
+    def test_missing(self):
+        class DefaultChainMap(ChainMap):
+            def __missing__(self, key):
+                return 999
+        d = DefaultChainMap(dict(a=1, b=2), dict(b=20, c=30))
+        for k, v in dict(a=1, b=2, c=30, d=999).items():
+            self.assertEqual(d[k], v)                                  # check __getitem__ w/missing
+        for k, v in dict(a=1, b=2, c=30, d=77).items():
+            self.assertEqual(d.get(k, 77), v)                          # check get() w/ missing
+        for k, v in dict(a=True, b=True, c=True, d=False).items():
+            self.assertEqual(k in d, v)                                # check __contains__ w/missing
+        self.assertEqual(d.pop('a', 1001), 1, d)
+        self.assertEqual(d.pop('a', 1002), 1002)                       # check pop() w/missing
+        self.assertEqual(d.popitem(), ('b', 2))                        # check popitem() w/missing
+        with self.assertRaises(KeyError):
+            d.popitem()
+
+    def test_order_preservation(self):
+        d = ChainMap(
+                OrderedDict(j=0, h=88888),
+                OrderedDict(),
+                OrderedDict(i=9999, d=4444, c=3333),
+                OrderedDict(f=666, b=222, g=777, c=333, h=888),
+                OrderedDict(),
+                OrderedDict(e=55, b=22),
+                OrderedDict(a=1, b=2, c=3, d=4, e=5),
+                OrderedDict(),
+            )
+        self.assertEqual(''.join(d), 'abcdefghij')
+        self.assertEqual(list(d.items()),
+            [('a', 1), ('b', 222), ('c', 3333), ('d', 4444),
+             ('e', 55), ('f', 666), ('g', 777), ('h', 88888),
+             ('i', 9999), ('j', 0)])
+
+    def test_dict_coercion(self):
+        d = ChainMap(dict(a=1, b=2), dict(b=20, c=30))
+        self.assertEqual(dict(d), dict(a=1, b=2, c=30))
+        self.assertEqual(dict(d.items()), dict(a=1, b=2, c=30))
+
+    def test_new_child(self):
+        'Tests for changes for issue #16613.'
+        c = ChainMap()
+        c['a'] = 1
+        c['b'] = 2
+        m = {'b':20, 'c': 30}
+        d = c.new_child(m)
+        self.assertEqual(d.maps, [{'b':20, 'c':30}, {'a':1, 'b':2}])  # check internal state
+        self.assertIs(m, d.maps[0])
+
+        # Use a different map than a dict
+        class lowerdict(dict):
+            def __getitem__(self, key):
+                if isinstance(key, str):
+                    key = key.lower()
+                return dict.__getitem__(self, key)
+            def __contains__(self, key):
+                if isinstance(key, str):
+                    key = key.lower()
+                return dict.__contains__(self, key)
+
+        c = ChainMap()
+        c['a'] = 1
+        c['b'] = 2
+        m = lowerdict(b=20, c=30)
+        d = c.new_child(m)
+        self.assertIs(m, d.maps[0])
+        for key in 'abc':                                             # check contains
+            self.assertIn(key, d)
+        for k, v in dict(a=1, B=20, C=30, z=100).items():             # check get
+            self.assertEqual(d.get(k, 100), v)
+
+
+################################################################################
+### Named Tuples
+################################################################################
+
+TestNT = namedtuple('TestNT', 'x y z')    # type used for pickle tests
+
+class TestNamedTuple(unittest.TestCase):
+
+    def test_factory(self):
+        Point = namedtuple('Point', 'x y')
+        self.assertEqual(Point.__name__, 'Point')
+        self.assertEqual(Point.__slots__, ())
+        self.assertEqual(Point.__module__, __name__)
+        self.assertEqual(Point.__getitem__, tuple.__getitem__)
+        self.assertEqual(Point._fields, ('x', 'y'))
+
+        self.assertRaises(ValueError, namedtuple, 'abc%', 'efg ghi')       # type has non-alpha char
+        self.assertRaises(ValueError, namedtuple, 'class', 'efg ghi')      # type has keyword
+        self.assertRaises(ValueError, namedtuple, '9abc', 'efg ghi')       # type starts with digit
+
+        self.assertRaises(ValueError, namedtuple, 'abc', 'efg g%hi')       # field with non-alpha char
+        self.assertRaises(ValueError, namedtuple, 'abc', 'abc class')      # field has keyword
+        self.assertRaises(ValueError, namedtuple, 'abc', '8efg 9ghi')      # field starts with digit
+        self.assertRaises(ValueError, namedtuple, 'abc', '_efg ghi')       # field with leading underscore
+        self.assertRaises(ValueError, namedtuple, 'abc', 'efg efg ghi')    # duplicate field
+
+        namedtuple('Point0', 'x1 y2')   # Verify that numbers are allowed in names
+        namedtuple('_', 'a b c')        # Test leading underscores in a typename
+
+        nt = namedtuple('nt', 'the quick brown fox')                       # check unicode input
+        self.assertNotIn("u'", repr(nt._fields))
+        nt = namedtuple('nt', ('the', 'quick'))                           # check unicode input
+        self.assertNotIn("u'", repr(nt._fields))
+
+        self.assertRaises(TypeError, Point._make, [11])                     # catch too few args
+        self.assertRaises(TypeError, Point._make, [11, 22, 33])             # catch too many args
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_defaults(self):
+        Point = namedtuple('Point', 'x y', defaults=(10, 20))              # 2 defaults
+        self.assertEqual(Point._field_defaults, {'x': 10, 'y': 20})
+        self.assertEqual(Point(1, 2), (1, 2))
+        self.assertEqual(Point(1), (1, 20))
+        self.assertEqual(Point(), (10, 20))
+
+        Point = namedtuple('Point', 'x y', defaults=(20,))                 # 1 default
+        self.assertEqual(Point._field_defaults, {'y': 20})
+        self.assertEqual(Point(1, 2), (1, 2))
+        self.assertEqual(Point(1), (1, 20))
+
+        Point = namedtuple('Point', 'x y', defaults=())                     # 0 defaults
+        self.assertEqual(Point._field_defaults, {})
+        self.assertEqual(Point(1, 2), (1, 2))
+        with self.assertRaises(TypeError):
+            Point(1)
+
+        with self.assertRaises(TypeError):                                  # catch too few args
+            Point()
+        with self.assertRaises(TypeError):                                  # catch too many args
+            Point(1, 2, 3)
+        with self.assertRaises(TypeError):                                  # too many defaults
+            Point = namedtuple('Point', 'x y', defaults=(10, 20, 30))
+        with self.assertRaises(TypeError):                                  # non-iterable defaults
+            Point = namedtuple('Point', 'x y', defaults=10)
+        with self.assertRaises(TypeError):                                  # another non-iterable default
+            Point = namedtuple('Point', 'x y', defaults=False)
+
+        Point = namedtuple('Point', 'x y', defaults=None)                   # default is None
+        self.assertEqual(Point._field_defaults, {})
+        self.assertIsNone(Point.__new__.__defaults__, None)
+        self.assertEqual(Point(10, 20), (10, 20))
+        with self.assertRaises(TypeError):                                  # catch too few args
+            Point(10)
+
+        Point = namedtuple('Point', 'x y', defaults=[10, 20])               # allow non-tuple iterable
+        self.assertEqual(Point._field_defaults, {'x': 10, 'y': 20})
+        self.assertEqual(Point.__new__.__defaults__, (10, 20))
+        self.assertEqual(Point(1, 2), (1, 2))
+        self.assertEqual(Point(1), (1, 20))
+        self.assertEqual(Point(), (10, 20))
+
+        Point = namedtuple('Point', 'x y', defaults=iter([10, 20]))         # allow plain iterator
+        self.assertEqual(Point._field_defaults, {'x': 10, 'y': 20})
+        self.assertEqual(Point.__new__.__defaults__, (10, 20))
+        self.assertEqual(Point(1, 2), (1, 2))
+        self.assertEqual(Point(1), (1, 20))
+        self.assertEqual(Point(), (10, 20))
+
+    def test_readonly(self):
+        Point = namedtuple('Point', 'x y')
+        p = Point(11, 22)
+        with self.assertRaises(AttributeError):
+            p.x = 33
+        with self.assertRaises(AttributeError):
+            del p.x
+        with self.assertRaises(TypeError):
+            p[0] = 33
+        with self.assertRaises(TypeError):
+            del p[0]
+        self.assertEqual(p.x, 11)
+        self.assertEqual(p[0], 11)
+
+    @unittest.skipIf(sys.flags.optimize >= 2,
+                     "Docstrings are omitted with -O2 and above")
+    def test_factory_doc_attr(self):
+        Point = namedtuple('Point', 'x y')
+        self.assertEqual(Point.__doc__, 'Point(x, y)')
+        Point.__doc__ = '2D point'
+        self.assertEqual(Point.__doc__, '2D point')
+
+    @unittest.skipIf(sys.flags.optimize >= 2,
+                     "Docstrings are omitted with -O2 and above")
+    def test_field_doc(self):
+        Point = namedtuple('Point', 'x y')
+        self.assertEqual(Point.x.__doc__, 'Alias for field number 0')
+        self.assertEqual(Point.y.__doc__, 'Alias for field number 1')
+        Point.x.__doc__ = 'docstring for Point.x'
+        self.assertEqual(Point.x.__doc__, 'docstring for Point.x')
+        # namedtuple can mutate doc of descriptors independently
+        Vector = namedtuple('Vector', 'x y')
+        self.assertEqual(Vector.x.__doc__, 'Alias for field number 0')
+        Vector.x.__doc__ = 'docstring for Vector.x'
+        self.assertEqual(Vector.x.__doc__, 'docstring for Vector.x')
+
+    @support.cpython_only
+    @unittest.skipIf(sys.flags.optimize >= 2,
+                     "Docstrings are omitted with -O2 and above")
+    def test_field_doc_reuse(self):
+        P = namedtuple('P', ['m', 'n'])
+        Q = namedtuple('Q', ['o', 'p'])
+        self.assertIs(P.m.__doc__, Q.o.__doc__)
+        self.assertIs(P.n.__doc__, Q.p.__doc__)
+
+    def test_name_fixer(self):
+        for spec, renamed in [
+            [('efg', 'g%hi'),  ('efg', '_1')],                              # field with non-alpha char
+            [('abc', 'class'), ('abc', '_1')],                              # field has keyword
+            [('8efg', '9ghi'), ('_0', '_1')],                               # field starts with digit
+            [('abc', '_efg'), ('abc', '_1')],                               # field with leading underscore
+            [('abc', 'efg', 'efg', 'ghi'), ('abc', 'efg', '_2', 'ghi')],    # duplicate field
+            [('abc', '', 'x'), ('abc', '_1', 'x')],                         # fieldname is a space
+        ]:
+            self.assertEqual(namedtuple('NT', spec, rename=True)._fields, renamed)
+
+    def test_module_parameter(self):
+        NT = namedtuple('NT', ['x', 'y'], module=collections)
+        self.assertEqual(NT.__module__, collections)
+
+    def test_instance(self):
+        Point = namedtuple('Point', 'x y')
+        p = Point(11, 22)
+        self.assertEqual(p, Point(x=11, y=22))
+        self.assertEqual(p, Point(11, y=22))
+        self.assertEqual(p, Point(y=22, x=11))
+        self.assertEqual(p, Point(*(11, 22)))
+        self.assertEqual(p, Point(**dict(x=11, y=22)))
+        self.assertRaises(TypeError, Point, 1)          # too few args
+        self.assertRaises(TypeError, Point, 1, 2, 3)    # too many args
+        with self.assertRaises(TypeError):              # wrong keyword argument
+            Point(XXX=1, y=2)
+        with self.assertRaises(TypeError):              # missing keyword argument
+            Point(x=1)
+        self.assertEqual(repr(p), 'Point(x=11, y=22)')
+        self.assertNotIn('__weakref__', dir(p))
+        self.assertEqual(p, Point._make([11, 22]))      # test _make classmethod
+        self.assertEqual(p._fields, ('x', 'y'))         # test _fields attribute
+        self.assertEqual(p._replace(x=1), (1, 22))      # test _replace method
+        self.assertEqual(p._asdict(), dict(x=11, y=22)) # test _asdict method
+
+        try:
+            p._replace(x=1, error=2)
+        except ValueError:
+            pass
+        else:
+            self._fail('Did not detect an incorrect fieldname')
+
+        # verify that field string can have commas
+        Point = namedtuple('Point', 'x, y')
+        p = Point(x=11, y=22)
+        self.assertEqual(repr(p), 'Point(x=11, y=22)')
+
+        # verify that fieldspec can be a non-string sequence
+        Point = namedtuple('Point', ('x', 'y'))
+        p = Point(x=11, y=22)
+        self.assertEqual(repr(p), 'Point(x=11, y=22)')
+
+    def test_tupleness(self):
+        Point = namedtuple('Point', 'x y')
+        p = Point(11, 22)
+
+        self.assertIsInstance(p, tuple)
+        self.assertEqual(p, (11, 22))                                       # matches a real tuple
+        self.assertEqual(tuple(p), (11, 22))                                # coercable to a real tuple
+        self.assertEqual(list(p), [11, 22])                                 # coercable to a list
+        self.assertEqual(max(p), 22)                                        # iterable
+        self.assertEqual(max(*p), 22)                                       # star-able
+        x, y = p
+        self.assertEqual(p, (x, y))                                         # unpacks like a tuple
+        self.assertEqual((p[0], p[1]), (11, 22))                            # indexable like a tuple
+        with self.assertRaises(IndexError):
+            p[3]
+        self.assertEqual(p[-1], 22)
+        self.assertEqual(hash(p), hash((11, 22)))
+
+        self.assertEqual(p.x, x)
+        self.assertEqual(p.y, y)
+        with self.assertRaises(AttributeError):
+            p.z
+
+    def test_odd_sizes(self):
+        Zero = namedtuple('Zero', '')
+        self.assertEqual(Zero(), ())
+        self.assertEqual(Zero._make([]), ())
+        self.assertEqual(repr(Zero()), 'Zero()')
+        self.assertEqual(Zero()._asdict(), {})
+        self.assertEqual(Zero()._fields, ())
+
+        Dot = namedtuple('Dot', 'd')
+        self.assertEqual(Dot(1), (1,))
+        self.assertEqual(Dot._make([1]), (1,))
+        self.assertEqual(Dot(1).d, 1)
+        self.assertEqual(repr(Dot(1)), 'Dot(d=1)')
+        self.assertEqual(Dot(1)._asdict(), {'d':1})
+        self.assertEqual(Dot(1)._replace(d=999), (999,))
+        self.assertEqual(Dot(1)._fields, ('d',))
+
+        n = 5000
+        names = list(set(''.join([choice(string.ascii_letters)
+                                  for j in range(10)]) for i in range(n)))
+        n = len(names)
+        Big = namedtuple('Big', names)
+        b = Big(*range(n))
+        self.assertEqual(b, tuple(range(n)))
+        self.assertEqual(Big._make(range(n)), tuple(range(n)))
+        for pos, name in enumerate(names):
+            self.assertEqual(getattr(b, name), pos)
+        repr(b)                                 # make sure repr() doesn't blow-up
+        d = b._asdict()
+        d_expected = dict(zip(names, range(n)))
+        self.assertEqual(d, d_expected)
+        b2 = b._replace(**dict([(names[1], 999),(names[-5], 42)]))
+        b2_expected = list(range(n))
+        b2_expected[1] = 999
+        b2_expected[-5] = 42
+        self.assertEqual(b2, tuple(b2_expected))
+        self.assertEqual(b._fields, tuple(names))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_pickle(self):
+        p = TestNT(x=10, y=20, z=30)
+        for module in (pickle,):
+            loads = getattr(module, 'loads')
+            dumps = getattr(module, 'dumps')
+            for protocol in range(-1, module.HIGHEST_PROTOCOL + 1):
+                q = loads(dumps(p, protocol))
+                self.assertEqual(p, q)
+                self.assertEqual(p._fields, q._fields)
+                self.assertNotIn(b'OrderedDict', dumps(p, protocol))
+
+    def test_copy(self):
+        p = TestNT(x=10, y=20, z=30)
+        for copier in copy.copy, copy.deepcopy:
+            q = copier(p)
+            self.assertEqual(p, q)
+            self.assertEqual(p._fields, q._fields)
+
+    def test_name_conflicts(self):
+        # Some names like "self", "cls", "tuple", "itemgetter", and "property"
+        # failed when used as field names.  Test to make sure these now work.
+        T = namedtuple('T', 'itemgetter property self cls tuple')
+        t = T(1, 2, 3, 4, 5)
+        self.assertEqual(t, (1,2,3,4,5))
+        newt = t._replace(itemgetter=10, property=20, self=30, cls=40, tuple=50)
+        self.assertEqual(newt, (10,20,30,40,50))
+
+       # Broader test of all interesting names taken from the code, old
+       # template, and an example
+        words = {'Alias', 'At', 'AttributeError', 'Build', 'Bypass', 'Create',
+        'Encountered', 'Expected', 'Field', 'For', 'Got', 'Helper',
+        'IronPython', 'Jython', 'KeyError', 'Make', 'Modify', 'Note',
+        'OrderedDict', 'Point', 'Return', 'Returns', 'Type', 'TypeError',
+        'Used', 'Validate', 'ValueError', 'Variables', 'a', 'accessible', 'add',
+        'added', 'all', 'also', 'an', 'arg_list', 'args', 'arguments',
+        'automatically', 'be', 'build', 'builtins', 'but', 'by', 'cannot',
+        'class_namespace', 'classmethod', 'cls', 'collections', 'convert',
+        'copy', 'created', 'creation', 'd', 'debugging', 'defined', 'dict',
+        'dictionary', 'doc', 'docstring', 'docstrings', 'duplicate', 'effect',
+        'either', 'enumerate', 'environments', 'error', 'example', 'exec', 'f',
+        'f_globals', 'field', 'field_names', 'fields', 'formatted', 'frame',
+        'function', 'functions', 'generate', 'get', 'getter', 'got', 'greater',
+        'has', 'help', 'identifiers', 'index', 'indexable', 'instance',
+        'instantiate', 'interning', 'introspection', 'isidentifier',
+        'isinstance', 'itemgetter', 'iterable', 'join', 'keyword', 'keywords',
+        'kwds', 'len', 'like', 'list', 'map', 'maps', 'message', 'metadata',
+        'method', 'methods', 'module', 'module_name', 'must', 'name', 'named',
+        'namedtuple', 'namedtuple_', 'names', 'namespace', 'needs', 'new',
+        'nicely', 'num_fields', 'number', 'object', 'of', 'operator', 'option',
+        'p', 'particular', 'pickle', 'pickling', 'plain', 'pop', 'positional',
+        'property', 'r', 'regular', 'rename', 'replace', 'replacing', 'repr',
+        'repr_fmt', 'representation', 'result', 'reuse_itemgetter', 's', 'seen',
+        'self', 'sequence', 'set', 'side', 'specified', 'split', 'start',
+        'startswith', 'step', 'str', 'string', 'strings', 'subclass', 'sys',
+        'targets', 'than', 'the', 'their', 'this', 'to', 'tuple', 'tuple_new',
+        'type', 'typename', 'underscore', 'unexpected', 'unpack', 'up', 'use',
+        'used', 'user', 'valid', 'values', 'variable', 'verbose', 'where',
+        'which', 'work', 'x', 'y', 'z', 'zip'}
+        T = namedtuple('T', words)
+        # test __new__
+        values = tuple(range(len(words)))
+        t = T(*values)
+        self.assertEqual(t, values)
+        t = T(**dict(zip(T._fields, values)))
+        self.assertEqual(t, values)
+        # test _make
+        t = T._make(values)
+        self.assertEqual(t, values)
+        # exercise __repr__
+        repr(t)
+        # test _asdict
+        self.assertEqual(t._asdict(), dict(zip(T._fields, values)))
+        # test _replace
+        t = T._make(values)
+        newvalues = tuple(v*10 for v in values)
+        newt = t._replace(**dict(zip(T._fields, newvalues)))
+        self.assertEqual(newt, newvalues)
+        # test _fields
+        self.assertEqual(T._fields, tuple(words))
+        # test __getnewargs__
+        self.assertEqual(t.__getnewargs__(), values)
+
+    def test_repr(self):
+        A = namedtuple('A', 'x')
+        self.assertEqual(repr(A(1)), 'A(x=1)')
+        # repr should show the name of the subclass
+        class B(A):
+            pass
+        self.assertEqual(repr(B(1)), 'B(x=1)')
+
+    def test_keyword_only_arguments(self):
+        # See issue 25628
+        with self.assertRaises(TypeError):
+            NT = namedtuple('NT', ['x', 'y'], True)
+
+        NT = namedtuple('NT', ['abc', 'def'], rename=True)
+        self.assertEqual(NT._fields, ('abc', '_1'))
+        with self.assertRaises(TypeError):
+            NT = namedtuple('NT', ['abc', 'def'], False, True)
+
+    def test_namedtuple_subclass_issue_24931(self):
+        class Point(namedtuple('_Point', ['x', 'y'])):
+            pass
+
+        a = Point(3, 4)
+        self.assertEqual(a._asdict(), OrderedDict([('x', 3), ('y', 4)]))
+
+        a.w = 5
+        self.assertEqual(a.__dict__, {'w': 5})
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_field_descriptor(self):
+        Point = namedtuple('Point', 'x y')
+        p = Point(11, 22)
+        self.assertTrue(inspect.isdatadescriptor(Point.x))
+        self.assertEqual(Point.x.__get__(p), 11)
+        self.assertRaises(AttributeError, Point.x.__set__, p, 33)
+        self.assertRaises(AttributeError, Point.x.__delete__, p)
+
+        class NewPoint(tuple):
+            x = pickle.loads(pickle.dumps(Point.x))
+            y = pickle.loads(pickle.dumps(Point.y))
+
+        np = NewPoint([1, 2])
+
+        self.assertEqual(np.x, 1)
+        self.assertEqual(np.y, 2)
+
+
+################################################################################
+### Abstract Base Classes
+################################################################################
+
+class ABCTestCase(unittest.TestCase):
+
+    def validate_abstract_methods(self, abc, *names):
+        methodstubs = dict.fromkeys(names, lambda s, *args: 0)
+
+        # everything should work will all required methods are present
+        C = type('C', (abc,), methodstubs)
+        C()
+
+        # instantiation should fail if a required method is missing
+        for name in names:
+            stubs = methodstubs.copy()
+            del stubs[name]
+            C = type('C', (abc,), stubs)
+            self.assertRaises(TypeError, C, name)
+
+    def validate_isinstance(self, abc, name):
+        stub = lambda s, *args: 0
+
+        C = type('C', (object,), {'__hash__': None})
+        setattr(C, name, stub)
+        self.assertIsInstance(C(), abc)
+        self.assertTrue(issubclass(C, abc))
+
+        C = type('C', (object,), {'__hash__': None})
+        self.assertNotIsInstance(C(), abc)
+        self.assertFalse(issubclass(C, abc))
+
+    def validate_comparison(self, instance):
+        ops = ['lt', 'gt', 'le', 'ge', 'ne', 'or', 'and', 'xor', 'sub']
+        operators = {}
+        for op in ops:
+            name = '__' + op + '__'
+            operators[name] = getattr(operator, name)
+
+        class Other:
+            def __init__(self):
+                self.right_side = False
+            def __eq__(self, other):
+                self.right_side = True
+                return True
+            __lt__ = __eq__
+            __gt__ = __eq__
+            __le__ = __eq__
+            __ge__ = __eq__
+            __ne__ = __eq__
+            __ror__ = __eq__
+            __rand__ = __eq__
+            __rxor__ = __eq__
+            __rsub__ = __eq__
+
+        for name, op in operators.items():
+            if not hasattr(instance, name):
+                continue
+            other = Other()
+            op(instance, other)
+            self.assertTrue(other.right_side,'Right side not called for %s.%s'
+                            % (type(instance), name))
+
+def _test_gen():
+    yield
+
+class TestOneTrickPonyABCs(ABCTestCase):
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Awaitable(self):
+        def gen():
+            yield
+
+        @types.coroutine
+        def coro():
+            yield
+
+        async def new_coro():
+            pass
+
+        class Bar:
+            def __await__(self):
+                yield
+
+        class MinimalCoro(Coroutine):
+            def send(self, value):
+                return value
+            def throw(self, typ, val=None, tb=None):
+                super().throw(typ, val, tb)
+            def __await__(self):
+                yield
+
+        non_samples = [None, int(), gen(), object()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Awaitable)
+            self.assertFalse(issubclass(type(x), Awaitable), repr(type(x)))
+
+        samples = [Bar(), MinimalCoro()]
+        for x in samples:
+            self.assertIsInstance(x, Awaitable)
+            self.assertTrue(issubclass(type(x), Awaitable))
+
+        c = coro()
+        # Iterable coroutines (generators with CO_ITERABLE_COROUTINE
+        # flag don't have '__await__' method, hence can't be instances
+        # of Awaitable. Use inspect.isawaitable to detect them.
+        self.assertNotIsInstance(c, Awaitable)
+
+        c = new_coro()
+        self.assertIsInstance(c, Awaitable)
+        c.close() # avoid RuntimeWarning that coro() was not awaited
+
+        class CoroLike: pass
+        Coroutine.register(CoroLike)
+        self.assertTrue(isinstance(CoroLike(), Awaitable))
+        self.assertTrue(issubclass(CoroLike, Awaitable))
+        CoroLike = None
+        support.gc_collect() # Kill CoroLike to clean-up ABCMeta cache
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Coroutine(self):
+        def gen():
+            yield
+
+        @types.coroutine
+        def coro():
+            yield
+
+        async def new_coro():
+            pass
+
+        class Bar:
+            def __await__(self):
+                yield
+
+        class MinimalCoro(Coroutine):
+            def send(self, value):
+                return value
+            def throw(self, typ, val=None, tb=None):
+                super().throw(typ, val, tb)
+            def __await__(self):
+                yield
+
+        non_samples = [None, int(), gen(), object(), Bar()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Coroutine)
+            self.assertFalse(issubclass(type(x), Coroutine), repr(type(x)))
+
+        samples = [MinimalCoro()]
+        for x in samples:
+            self.assertIsInstance(x, Awaitable)
+            self.assertTrue(issubclass(type(x), Awaitable))
+
+        c = coro()
+        # Iterable coroutines (generators with CO_ITERABLE_COROUTINE
+        # flag don't have '__await__' method, hence can't be instances
+        # of Coroutine. Use inspect.isawaitable to detect them.
+        self.assertNotIsInstance(c, Coroutine)
+
+        c = new_coro()
+        self.assertIsInstance(c, Coroutine)
+        c.close() # avoid RuntimeWarning that coro() was not awaited
+
+        class CoroLike:
+            def send(self, value):
+                pass
+            def throw(self, typ, val=None, tb=None):
+                pass
+            def close(self):
+                pass
+            def __await__(self):
+                pass
+        self.assertTrue(isinstance(CoroLike(), Coroutine))
+        self.assertTrue(issubclass(CoroLike, Coroutine))
+
+        class CoroLike:
+            def send(self, value):
+                pass
+            def close(self):
+                pass
+            def __await__(self):
+                pass
+        self.assertFalse(isinstance(CoroLike(), Coroutine))
+        self.assertFalse(issubclass(CoroLike, Coroutine))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Hashable(self):
+        # Check some non-hashables
+        non_samples = [bytearray(), list(), set(), dict()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Hashable)
+            self.assertFalse(issubclass(type(x), Hashable), repr(type(x)))
+        # Check some hashables
+        samples = [None,
+                   int(), float(), complex(),
+                   str(),
+                   tuple(), frozenset(),
+                   int, list, object, type, bytes()
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Hashable)
+            self.assertTrue(issubclass(type(x), Hashable), repr(type(x)))
+        self.assertRaises(TypeError, Hashable)
+        # Check direct subclassing
+        class H(Hashable):
+            def __hash__(self):
+                return super().__hash__()
+        self.assertEqual(hash(H()), 0)
+        self.assertFalse(issubclass(int, H))
+        self.validate_abstract_methods(Hashable, '__hash__')
+        self.validate_isinstance(Hashable, '__hash__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_AsyncIterable(self):
+        class AI:
+            def __aiter__(self):
+                return self
+        self.assertTrue(isinstance(AI(), AsyncIterable))
+        self.assertTrue(issubclass(AI, AsyncIterable))
+        # Check some non-iterables
+        non_samples = [None, object, []]
+        for x in non_samples:
+            self.assertNotIsInstance(x, AsyncIterable)
+            self.assertFalse(issubclass(type(x), AsyncIterable), repr(type(x)))
+        self.validate_abstract_methods(AsyncIterable, '__aiter__')
+        self.validate_isinstance(AsyncIterable, '__aiter__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_AsyncIterator(self):
+        class AI:
+            def __aiter__(self):
+                return self
+            async def __anext__(self):
+                raise StopAsyncIteration
+        self.assertTrue(isinstance(AI(), AsyncIterator))
+        self.assertTrue(issubclass(AI, AsyncIterator))
+        non_samples = [None, object, []]
+        # Check some non-iterables
+        for x in non_samples:
+            self.assertNotIsInstance(x, AsyncIterator)
+            self.assertFalse(issubclass(type(x), AsyncIterator), repr(type(x)))
+        # Similarly to regular iterators (see issue 10565)
+        class AnextOnly:
+            async def __anext__(self):
+                raise StopAsyncIteration
+        self.assertNotIsInstance(AnextOnly(), AsyncIterator)
+        self.validate_abstract_methods(AsyncIterator, '__anext__', '__aiter__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Iterable(self):
+        # Check some non-iterables
+        non_samples = [None, 42, 3.14, 1j]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Iterable)
+            self.assertFalse(issubclass(type(x), Iterable), repr(type(x)))
+        # Check some iterables
+        samples = [bytes(), str(),
+                   tuple(), list(), set(), frozenset(), dict(),
+                   dict().keys(), dict().items(), dict().values(),
+                   _test_gen(),
+                   (x for x in []),
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Iterable)
+            self.assertTrue(issubclass(type(x), Iterable), repr(type(x)))
+        # Check direct subclassing
+        class I(Iterable):
+            def __iter__(self):
+                return super().__iter__()
+        self.assertEqual(list(I()), [])
+        self.assertFalse(issubclass(str, I))
+        self.validate_abstract_methods(Iterable, '__iter__')
+        self.validate_isinstance(Iterable, '__iter__')
+        # Check None blocking
+        class It:
+            def __iter__(self): return iter([])
+        class ItBlocked(It):
+            __iter__ = None
+        self.assertTrue(issubclass(It, Iterable))
+        self.assertTrue(isinstance(It(), Iterable))
+        self.assertFalse(issubclass(ItBlocked, Iterable))
+        self.assertFalse(isinstance(ItBlocked(), Iterable))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Reversible(self):
+        # Check some non-reversibles
+        non_samples = [None, 42, 3.14, 1j, set(), frozenset()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Reversible)
+            self.assertFalse(issubclass(type(x), Reversible), repr(type(x)))
+        # Check some non-reversible iterables
+        non_reversibles = [_test_gen(), (x for x in []), iter([]), reversed([])]
+        for x in non_reversibles:
+            self.assertNotIsInstance(x, Reversible)
+            self.assertFalse(issubclass(type(x), Reversible), repr(type(x)))
+        # Check some reversible iterables
+        samples = [bytes(), str(), tuple(), list(), OrderedDict(),
+                   OrderedDict().keys(), OrderedDict().items(),
+                   OrderedDict().values(), Counter(), Counter().keys(),
+                   Counter().items(), Counter().values(), dict(),
+                   dict().keys(), dict().items(), dict().values()]
+        for x in samples:
+            self.assertIsInstance(x, Reversible)
+            self.assertTrue(issubclass(type(x), Reversible), repr(type(x)))
+        # Check also Mapping, MutableMapping, and Sequence
+        self.assertTrue(issubclass(Sequence, Reversible), repr(Sequence))
+        self.assertFalse(issubclass(Mapping, Reversible), repr(Mapping))
+        self.assertFalse(issubclass(MutableMapping, Reversible), repr(MutableMapping))
+        # Check direct subclassing
+        class R(Reversible):
+            def __iter__(self):
+                return iter(list())
+            def __reversed__(self):
+                return iter(list())
+        self.assertEqual(list(reversed(R())), [])
+        self.assertFalse(issubclass(float, R))
+        self.validate_abstract_methods(Reversible, '__reversed__', '__iter__')
+        # Check reversible non-iterable (which is not Reversible)
+        class RevNoIter:
+            def __reversed__(self): return reversed([])
+        class RevPlusIter(RevNoIter):
+            def __iter__(self): return iter([])
+        self.assertFalse(issubclass(RevNoIter, Reversible))
+        self.assertFalse(isinstance(RevNoIter(), Reversible))
+        self.assertTrue(issubclass(RevPlusIter, Reversible))
+        self.assertTrue(isinstance(RevPlusIter(), Reversible))
+        # Check None blocking
+        class Rev:
+            def __iter__(self): return iter([])
+            def __reversed__(self): return reversed([])
+        class RevItBlocked(Rev):
+            __iter__ = None
+        class RevRevBlocked(Rev):
+            __reversed__ = None
+        self.assertTrue(issubclass(Rev, Reversible))
+        self.assertTrue(isinstance(Rev(), Reversible))
+        self.assertFalse(issubclass(RevItBlocked, Reversible))
+        self.assertFalse(isinstance(RevItBlocked(), Reversible))
+        self.assertFalse(issubclass(RevRevBlocked, Reversible))
+        self.assertFalse(isinstance(RevRevBlocked(), Reversible))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Collection(self):
+        # Check some non-collections
+        non_collections = [None, 42, 3.14, 1j, lambda x: 2*x]
+        for x in non_collections:
+            self.assertNotIsInstance(x, Collection)
+            self.assertFalse(issubclass(type(x), Collection), repr(type(x)))
+        # Check some non-collection iterables
+        non_col_iterables = [_test_gen(), iter(b''), iter(bytearray()),
+                             (x for x in [])]
+        for x in non_col_iterables:
+            self.assertNotIsInstance(x, Collection)
+            self.assertFalse(issubclass(type(x), Collection), repr(type(x)))
+        # Check some collections
+        samples = [set(), frozenset(), dict(), bytes(), str(), tuple(),
+                   list(), dict().keys(), dict().items(), dict().values()]
+        for x in samples:
+            self.assertIsInstance(x, Collection)
+            self.assertTrue(issubclass(type(x), Collection), repr(type(x)))
+        # Check also Mapping, MutableMapping, etc.
+        self.assertTrue(issubclass(Sequence, Collection), repr(Sequence))
+        self.assertTrue(issubclass(Mapping, Collection), repr(Mapping))
+        self.assertTrue(issubclass(MutableMapping, Collection),
+                                    repr(MutableMapping))
+        self.assertTrue(issubclass(Set, Collection), repr(Set))
+        self.assertTrue(issubclass(MutableSet, Collection), repr(MutableSet))
+        self.assertTrue(issubclass(Sequence, Collection), repr(MutableSet))
+        # Check direct subclassing
+        class Col(Collection):
+            def __iter__(self):
+                return iter(list())
+            def __len__(self):
+                return 0
+            def __contains__(self, item):
+                return False
+        class DerCol(Col): pass
+        self.assertEqual(list(iter(Col())), [])
+        self.assertFalse(issubclass(list, Col))
+        self.assertFalse(issubclass(set, Col))
+        self.assertFalse(issubclass(float, Col))
+        self.assertEqual(list(iter(DerCol())), [])
+        self.assertFalse(issubclass(list, DerCol))
+        self.assertFalse(issubclass(set, DerCol))
+        self.assertFalse(issubclass(float, DerCol))
+        self.validate_abstract_methods(Collection, '__len__', '__iter__',
+                                                   '__contains__')
+        # Check sized container non-iterable (which is not Collection) etc.
+        class ColNoIter:
+            def __len__(self): return 0
+            def __contains__(self, item): return False
+        class ColNoSize:
+            def __iter__(self): return iter([])
+            def __contains__(self, item): return False
+        class ColNoCont:
+            def __iter__(self): return iter([])
+            def __len__(self): return 0
+        self.assertFalse(issubclass(ColNoIter, Collection))
+        self.assertFalse(isinstance(ColNoIter(), Collection))
+        self.assertFalse(issubclass(ColNoSize, Collection))
+        self.assertFalse(isinstance(ColNoSize(), Collection))
+        self.assertFalse(issubclass(ColNoCont, Collection))
+        self.assertFalse(isinstance(ColNoCont(), Collection))
+        # Check None blocking
+        class SizeBlock:
+            def __iter__(self): return iter([])
+            def __contains__(self): return False
+            __len__ = None
+        class IterBlock:
+            def __len__(self): return 0
+            def __contains__(self): return True
+            __iter__ = None
+        self.assertFalse(issubclass(SizeBlock, Collection))
+        self.assertFalse(isinstance(SizeBlock(), Collection))
+        self.assertFalse(issubclass(IterBlock, Collection))
+        self.assertFalse(isinstance(IterBlock(), Collection))
+        # Check None blocking in subclass
+        class ColImpl:
+            def __iter__(self):
+                return iter(list())
+            def __len__(self):
+                return 0
+            def __contains__(self, item):
+                return False
+        class NonCol(ColImpl):
+            __contains__ = None
+        self.assertFalse(issubclass(NonCol, Collection))
+        self.assertFalse(isinstance(NonCol(), Collection))
+
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Iterator(self):
+        non_samples = [None, 42, 3.14, 1j, b"", "", (), [], {}, set()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Iterator)
+            self.assertFalse(issubclass(type(x), Iterator), repr(type(x)))
+        samples = [iter(bytes()), iter(str()),
+                   iter(tuple()), iter(list()), iter(dict()),
+                   iter(set()), iter(frozenset()),
+                   iter(dict().keys()), iter(dict().items()),
+                   iter(dict().values()),
+                   _test_gen(),
+                   (x for x in []),
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Iterator)
+            self.assertTrue(issubclass(type(x), Iterator), repr(type(x)))
+        self.validate_abstract_methods(Iterator, '__next__', '__iter__')
+
+        # Issue 10565
+        class NextOnly:
+            def __next__(self):
+                yield 1
+                return
+        self.assertNotIsInstance(NextOnly(), Iterator)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Generator(self):
+        class NonGen1:
+            def __iter__(self): return self
+            def __next__(self): return None
+            def close(self): pass
+            def throw(self, typ, val=None, tb=None): pass
+
+        class NonGen2:
+            def __iter__(self): return self
+            def __next__(self): return None
+            def close(self): pass
+            def send(self, value): return value
+
+        class NonGen3:
+            def close(self): pass
+            def send(self, value): return value
+            def throw(self, typ, val=None, tb=None): pass
+
+        non_samples = [
+            None, 42, 3.14, 1j, b"", "", (), [], {}, set(),
+            iter(()), iter([]), NonGen1(), NonGen2(), NonGen3()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Generator)
+            self.assertFalse(issubclass(type(x), Generator), repr(type(x)))
+
+        class Gen:
+            def __iter__(self): return self
+            def __next__(self): return None
+            def close(self): pass
+            def send(self, value): return value
+            def throw(self, typ, val=None, tb=None): pass
+
+        class MinimalGen(Generator):
+            def send(self, value):
+                return value
+            def throw(self, typ, val=None, tb=None):
+                super().throw(typ, val, tb)
+
+        def gen():
+            yield 1
+
+        samples = [gen(), (lambda: (yield))(), Gen(), MinimalGen()]
+        for x in samples:
+            self.assertIsInstance(x, Iterator)
+            self.assertIsInstance(x, Generator)
+            self.assertTrue(issubclass(type(x), Generator), repr(type(x)))
+        self.validate_abstract_methods(Generator, 'send', 'throw')
+
+        # mixin tests
+        mgen = MinimalGen()
+        self.assertIs(mgen, iter(mgen))
+        self.assertIs(mgen.send(None), next(mgen))
+        self.assertEqual(2, mgen.send(2))
+        self.assertIsNone(mgen.close())
+        self.assertRaises(ValueError, mgen.throw, ValueError)
+        self.assertRaisesRegex(ValueError, "^huhu$",
+                               mgen.throw, ValueError, ValueError("huhu"))
+        self.assertRaises(StopIteration, mgen.throw, StopIteration())
+
+        class FailOnClose(Generator):
+            def send(self, value): return value
+            def throw(self, *args): raise ValueError
+
+        self.assertRaises(ValueError, FailOnClose().close)
+
+        class IgnoreGeneratorExit(Generator):
+            def send(self, value): return value
+            def throw(self, *args): pass
+
+        self.assertRaises(RuntimeError, IgnoreGeneratorExit().close)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_AsyncGenerator(self):
+        class NonAGen1:
+            def __aiter__(self): return self
+            def __anext__(self): return None
+            def aclose(self): pass
+            def athrow(self, typ, val=None, tb=None): pass
+
+        class NonAGen2:
+            def __aiter__(self): return self
+            def __anext__(self): return None
+            def aclose(self): pass
+            def asend(self, value): return value
+
+        class NonAGen3:
+            def aclose(self): pass
+            def asend(self, value): return value
+            def athrow(self, typ, val=None, tb=None): pass
+
+        non_samples = [
+            None, 42, 3.14, 1j, b"", "", (), [], {}, set(),
+            iter(()), iter([]), NonAGen1(), NonAGen2(), NonAGen3()]
+        for x in non_samples:
+            self.assertNotIsInstance(x, AsyncGenerator)
+            self.assertFalse(issubclass(type(x), AsyncGenerator), repr(type(x)))
+
+        class Gen:
+            def __aiter__(self): return self
+            async def __anext__(self): return None
+            async def aclose(self): pass
+            async def asend(self, value): return value
+            async def athrow(self, typ, val=None, tb=None): pass
+
+        class MinimalAGen(AsyncGenerator):
+            async def asend(self, value):
+                return value
+            async def athrow(self, typ, val=None, tb=None):
+                await super().athrow(typ, val, tb)
+
+        async def gen():
+            yield 1
+
+        samples = [gen(), Gen(), MinimalAGen()]
+        for x in samples:
+            self.assertIsInstance(x, AsyncIterator)
+            self.assertIsInstance(x, AsyncGenerator)
+            self.assertTrue(issubclass(type(x), AsyncGenerator), repr(type(x)))
+        self.validate_abstract_methods(AsyncGenerator, 'asend', 'athrow')
+
+        def run_async(coro):
+            result = None
+            while True:
+                try:
+                    coro.send(None)
+                except StopIteration as ex:
+                    result = ex.args[0] if ex.args else None
+                    break
+            return result
+
+        # mixin tests
+        mgen = MinimalAGen()
+        self.assertIs(mgen, mgen.__aiter__())
+        self.assertIs(run_async(mgen.asend(None)), run_async(mgen.__anext__()))
+        self.assertEqual(2, run_async(mgen.asend(2)))
+        self.assertIsNone(run_async(mgen.aclose()))
+        with self.assertRaises(ValueError):
+            run_async(mgen.athrow(ValueError))
+
+        class FailOnClose(AsyncGenerator):
+            async def asend(self, value): return value
+            async def athrow(self, *args): raise ValueError
+
+        with self.assertRaises(ValueError):
+            run_async(FailOnClose().aclose())
+
+        class IgnoreGeneratorExit(AsyncGenerator):
+            async def asend(self, value): return value
+            async def athrow(self, *args): pass
+
+        with self.assertRaises(RuntimeError):
+            run_async(IgnoreGeneratorExit().aclose())
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Sized(self):
+        non_samples = [None, 42, 3.14, 1j,
+                       _test_gen(),
+                       (x for x in []),
+                       ]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Sized)
+            self.assertFalse(issubclass(type(x), Sized), repr(type(x)))
+        samples = [bytes(), str(),
+                   tuple(), list(), set(), frozenset(), dict(),
+                   dict().keys(), dict().items(), dict().values(),
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Sized)
+            self.assertTrue(issubclass(type(x), Sized), repr(type(x)))
+        self.validate_abstract_methods(Sized, '__len__')
+        self.validate_isinstance(Sized, '__len__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Container(self):
+        non_samples = [None, 42, 3.14, 1j,
+                       _test_gen(),
+                       (x for x in []),
+                       ]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Container)
+            self.assertFalse(issubclass(type(x), Container), repr(type(x)))
+        samples = [bytes(), str(),
+                   tuple(), list(), set(), frozenset(), dict(),
+                   dict().keys(), dict().items(),
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Container)
+            self.assertTrue(issubclass(type(x), Container), repr(type(x)))
+        self.validate_abstract_methods(Container, '__contains__')
+        self.validate_isinstance(Container, '__contains__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Callable(self):
+        non_samples = [None, 42, 3.14, 1j,
+                       "", b"", (), [], {}, set(),
+                       _test_gen(),
+                       (x for x in []),
+                       ]
+        for x in non_samples:
+            self.assertNotIsInstance(x, Callable)
+            self.assertFalse(issubclass(type(x), Callable), repr(type(x)))
+        samples = [lambda: None,
+                   type, int, object,
+                   len,
+                   list.append, [].append,
+                   ]
+        for x in samples:
+            self.assertIsInstance(x, Callable)
+            self.assertTrue(issubclass(type(x), Callable), repr(type(x)))
+        self.validate_abstract_methods(Callable, '__call__')
+        self.validate_isinstance(Callable, '__call__')
+
+    def test_direct_subclassing(self):
+        for B in Hashable, Iterable, Iterator, Reversible, Sized, Container, Callable:
+            class C(B):
+                pass
+            self.assertTrue(issubclass(C, B))
+            self.assertFalse(issubclass(int, C))
+
+    def test_registration(self):
+        for B in Hashable, Iterable, Iterator, Reversible, Sized, Container, Callable:
+            class C:
+                __hash__ = None  # Make sure it isn't hashable by default
+            self.assertFalse(issubclass(C, B), B.__name__)
+            B.register(C)
+            self.assertTrue(issubclass(C, B))
+
+class WithSet(MutableSet):
+
+    def __init__(self, it=()):
+        self.data = set(it)
+
+    def __len__(self):
+        return len(self.data)
+
+    def __iter__(self):
+        return iter(self.data)
+
+    def __contains__(self, item):
+        return item in self.data
+
+    def add(self, item):
+        self.data.add(item)
+
+    def discard(self, item):
+        self.data.discard(item)
+
+class TestCollectionABCs(ABCTestCase):
+
+    # XXX For now, we only test some virtual inheritance properties.
+    # We should also test the proper behavior of the collection ABCs
+    # as real base classes or mix-in classes.
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Set(self):
+        for sample in [set, frozenset]:
+            self.assertIsInstance(sample(), Set)
+            self.assertTrue(issubclass(sample, Set))
+        self.validate_abstract_methods(Set, '__contains__', '__iter__', '__len__')
+        class MySet(Set):
+            def __contains__(self, x):
+                return False
+            def __len__(self):
+                return 0
+            def __iter__(self):
+                return iter([])
+        self.validate_comparison(MySet())
+
+    def test_hash_Set(self):
+        class OneTwoThreeSet(Set):
+            def __init__(self):
+                self.contents = [1, 2, 3]
+            def __contains__(self, x):
+                return x in self.contents
+            def __len__(self):
+                return len(self.contents)
+            def __iter__(self):
+                return iter(self.contents)
+            def __hash__(self):
+                return self._hash()
+        a, b = OneTwoThreeSet(), OneTwoThreeSet()
+        self.assertTrue(hash(a) == hash(b))
+
+    def test_isdisjoint_Set(self):
+        class MySet(Set):
+            def __init__(self, itr):
+                self.contents = itr
+            def __contains__(self, x):
+                return x in self.contents
+            def __iter__(self):
+                return iter(self.contents)
+            def __len__(self):
+                return len([x for x in self.contents])
+        s1 = MySet((1, 2, 3))
+        s2 = MySet((4, 5, 6))
+        s3 = MySet((1, 5, 6))
+        self.assertTrue(s1.isdisjoint(s2))
+        self.assertFalse(s1.isdisjoint(s3))
+
+    def test_equality_Set(self):
+        class MySet(Set):
+            def __init__(self, itr):
+                self.contents = itr
+            def __contains__(self, x):
+                return x in self.contents
+            def __iter__(self):
+                return iter(self.contents)
+            def __len__(self):
+                return len([x for x in self.contents])
+        s1 = MySet((1,))
+        s2 = MySet((1, 2))
+        s3 = MySet((3, 4))
+        s4 = MySet((3, 4))
+        self.assertTrue(s2 > s1)
+        self.assertTrue(s1 < s2)
+        self.assertFalse(s2 <= s1)
+        self.assertFalse(s2 <= s3)
+        self.assertFalse(s1 >= s2)
+        self.assertEqual(s3, s4)
+        self.assertNotEqual(s2, s3)
+
+    def test_arithmetic_Set(self):
+        class MySet(Set):
+            def __init__(self, itr):
+                self.contents = itr
+            def __contains__(self, x):
+                return x in self.contents
+            def __iter__(self):
+                return iter(self.contents)
+            def __len__(self):
+                return len([x for x in self.contents])
+        s1 = MySet((1, 2, 3))
+        s2 = MySet((3, 4, 5))
+        s3 = s1 & s2
+        self.assertEqual(s3, MySet((3,)))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_MutableSet(self):
+        self.assertIsInstance(set(), MutableSet)
+        self.assertTrue(issubclass(set, MutableSet))
+        self.assertNotIsInstance(frozenset(), MutableSet)
+        self.assertFalse(issubclass(frozenset, MutableSet))
+        self.validate_abstract_methods(MutableSet, '__contains__', '__iter__', '__len__',
+            'add', 'discard')
+
+    def test_issue_5647(self):
+        # MutableSet.__iand__ mutated the set during iteration
+        s = WithSet('abcd')
+        s &= WithSet('cdef')            # This used to fail
+        self.assertEqual(set(s), set('cd'))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_issue_4920(self):
+        # MutableSet.pop() method did not work
+        class MySet(MutableSet):
+            __slots__=['__s']
+            def __init__(self,items=None):
+                if items is None:
+                    items=[]
+                self.__s=set(items)
+            def __contains__(self,v):
+                return v in self.__s
+            def __iter__(self):
+                return iter(self.__s)
+            def __len__(self):
+                return len(self.__s)
+            def add(self,v):
+                result=v not in self.__s
+                self.__s.add(v)
+                return result
+            def discard(self,v):
+                result=v in self.__s
+                self.__s.discard(v)
+                return result
+            def __repr__(self):
+                return "MySet(%s)" % repr(list(self))
+        s = MySet([5,43,2,1])
+        self.assertEqual(s.pop(), 1)
+
+    def test_issue8750(self):
+        empty = WithSet()
+        full = WithSet(range(10))
+        s = WithSet(full)
+        s -= s
+        self.assertEqual(s, empty)
+        s = WithSet(full)
+        s ^= s
+        self.assertEqual(s, empty)
+        s = WithSet(full)
+        s &= s
+        self.assertEqual(s, full)
+        s |= s
+        self.assertEqual(s, full)
+
+    def test_issue16373(self):
+        # Recursion error comparing comparable and noncomparable
+        # Set instances
+        class MyComparableSet(Set):
+            def __contains__(self, x):
+                return False
+            def __len__(self):
+                return 0
+            def __iter__(self):
+                return iter([])
+        class MyNonComparableSet(Set):
+            def __contains__(self, x):
+                return False
+            def __len__(self):
+                return 0
+            def __iter__(self):
+                return iter([])
+            def __le__(self, x):
+                return NotImplemented
+            def __lt__(self, x):
+                return NotImplemented
+
+        cs = MyComparableSet()
+        ncs = MyNonComparableSet()
+        self.assertFalse(ncs < cs)
+        self.assertTrue(ncs <= cs)
+        self.assertFalse(ncs > cs)
+        self.assertTrue(ncs >= cs)
+
+    def test_issue26915(self):
+        # Container membership test should check identity first
+        class CustomEqualObject:
+            def __eq__(self, other):
+                return False
+        class CustomSequence(Sequence):
+            def __init__(self, seq):
+                self._seq = seq
+            def __getitem__(self, index):
+                return self._seq[index]
+            def __len__(self):
+                return len(self._seq)
+
+        nan = float('nan')
+        obj = CustomEqualObject()
+        seq = CustomSequence([nan, obj, nan])
+        containers = [
+            seq,
+            ItemsView({1: nan, 2: obj}),
+            ValuesView({1: nan, 2: obj})
+        ]
+        for container in containers:
+            for elem in container:
+                self.assertIn(elem, container)
+        self.assertEqual(seq.index(nan), 0)
+        self.assertEqual(seq.index(obj), 1)
+        self.assertEqual(seq.count(nan), 2)
+        self.assertEqual(seq.count(obj), 1)
+
+    def assertSameSet(self, s1, s2):
+        # coerce both to a real set then check equality
+        self.assertSetEqual(set(s1), set(s2))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Set_interoperability_with_real_sets(self):
+        # Issue: 8743
+        class ListSet(Set):
+            def __init__(self, elements=()):
+                self.data = []
+                for elem in elements:
+                    if elem not in self.data:
+                        self.data.append(elem)
+            def __contains__(self, elem):
+                return elem in self.data
+            def __iter__(self):
+                return iter(self.data)
+            def __len__(self):
+                return len(self.data)
+            def __repr__(self):
+                return 'Set({!r})'.format(self.data)
+
+        r1 = set('abc')
+        r2 = set('bcd')
+        r3 = set('abcde')
+        f1 = ListSet('abc')
+        f2 = ListSet('bcd')
+        f3 = ListSet('abcde')
+        l1 = list('abccba')
+        l2 = list('bcddcb')
+        l3 = list('abcdeedcba')
+
+        target = r1 & r2
+        self.assertSameSet(f1 & f2, target)
+        self.assertSameSet(f1 & r2, target)
+        self.assertSameSet(r2 & f1, target)
+        self.assertSameSet(f1 & l2, target)
+
+        target = r1 | r2
+        self.assertSameSet(f1 | f2, target)
+        self.assertSameSet(f1 | r2, target)
+        self.assertSameSet(r2 | f1, target)
+        self.assertSameSet(f1 | l2, target)
+
+        fwd_target = r1 - r2
+        rev_target = r2 - r1
+        self.assertSameSet(f1 - f2, fwd_target)
+        self.assertSameSet(f2 - f1, rev_target)
+        self.assertSameSet(f1 - r2, fwd_target)
+        self.assertSameSet(f2 - r1, rev_target)
+        self.assertSameSet(r1 - f2, fwd_target)
+        self.assertSameSet(r2 - f1, rev_target)
+        self.assertSameSet(f1 - l2, fwd_target)
+        self.assertSameSet(f2 - l1, rev_target)
+
+        target = r1 ^ r2
+        self.assertSameSet(f1 ^ f2, target)
+        self.assertSameSet(f1 ^ r2, target)
+        self.assertSameSet(r2 ^ f1, target)
+        self.assertSameSet(f1 ^ l2, target)
+
+        # Don't change the following to use assertLess or other
+        # "more specific" unittest assertions.  The current
+        # assertTrue/assertFalse style makes the pattern of test
+        # case combinations clear and allows us to know for sure
+        # the exact operator being invoked.
+
+        # proper subset
+        self.assertTrue(f1 < f3)
+        self.assertFalse(f1 < f1)
+        self.assertFalse(f1 < f2)
+        self.assertTrue(r1 < f3)
+        self.assertFalse(r1 < f1)
+        self.assertFalse(r1 < f2)
+        self.assertTrue(r1 < r3)
+        self.assertFalse(r1 < r1)
+        self.assertFalse(r1 < r2)
+        with self.assertRaises(TypeError):
+            f1 < l3
+        with self.assertRaises(TypeError):
+            f1 < l1
+        with self.assertRaises(TypeError):
+            f1 < l2
+
+        # any subset
+        self.assertTrue(f1 <= f3)
+        self.assertTrue(f1 <= f1)
+        self.assertFalse(f1 <= f2)
+        self.assertTrue(r1 <= f3)
+        self.assertTrue(r1 <= f1)
+        self.assertFalse(r1 <= f2)
+        self.assertTrue(r1 <= r3)
+        self.assertTrue(r1 <= r1)
+        self.assertFalse(r1 <= r2)
+        with self.assertRaises(TypeError):
+            f1 <= l3
+        with self.assertRaises(TypeError):
+            f1 <= l1
+        with self.assertRaises(TypeError):
+            f1 <= l2
+
+        # proper superset
+        self.assertTrue(f3 > f1)
+        self.assertFalse(f1 > f1)
+        self.assertFalse(f2 > f1)
+        self.assertTrue(r3 > r1)
+        self.assertFalse(f1 > r1)
+        self.assertFalse(f2 > r1)
+        self.assertTrue(r3 > r1)
+        self.assertFalse(r1 > r1)
+        self.assertFalse(r2 > r1)
+        with self.assertRaises(TypeError):
+            f1 > l3
+        with self.assertRaises(TypeError):
+            f1 > l1
+        with self.assertRaises(TypeError):
+            f1 > l2
+
+        # any superset
+        self.assertTrue(f3 >= f1)
+        self.assertTrue(f1 >= f1)
+        self.assertFalse(f2 >= f1)
+        self.assertTrue(r3 >= r1)
+        self.assertTrue(f1 >= r1)
+        self.assertFalse(f2 >= r1)
+        self.assertTrue(r3 >= r1)
+        self.assertTrue(r1 >= r1)
+        self.assertFalse(r2 >= r1)
+        with self.assertRaises(TypeError):
+            f1 >= l3
+        with self.assertRaises(TypeError):
+            f1 >=l1
+        with self.assertRaises(TypeError):
+            f1 >= l2
+
+        # equality
+        self.assertTrue(f1 == f1)
+        self.assertTrue(r1 == f1)
+        self.assertTrue(f1 == r1)
+        self.assertFalse(f1 == f3)
+        self.assertFalse(r1 == f3)
+        self.assertFalse(f1 == r3)
+        self.assertFalse(f1 == l3)
+        self.assertFalse(f1 == l1)
+        self.assertFalse(f1 == l2)
+
+        # inequality
+        self.assertFalse(f1 != f1)
+        self.assertFalse(r1 != f1)
+        self.assertFalse(f1 != r1)
+        self.assertTrue(f1 != f3)
+        self.assertTrue(r1 != f3)
+        self.assertTrue(f1 != r3)
+        self.assertTrue(f1 != l3)
+        self.assertTrue(f1 != l1)
+        self.assertTrue(f1 != l2)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Mapping(self):
+        for sample in [dict]:
+            self.assertIsInstance(sample(), Mapping)
+            self.assertTrue(issubclass(sample, Mapping))
+        self.validate_abstract_methods(Mapping, '__contains__', '__iter__', '__len__',
+            '__getitem__')
+        class MyMapping(Mapping):
+            def __len__(self):
+                return 0
+            def __getitem__(self, i):
+                raise IndexError
+            def __iter__(self):
+                return iter(())
+        self.validate_comparison(MyMapping())
+        self.assertRaises(TypeError, reversed, MyMapping())
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_MutableMapping(self):
+        for sample in [dict]:
+            self.assertIsInstance(sample(), MutableMapping)
+            self.assertTrue(issubclass(sample, MutableMapping))
+        self.validate_abstract_methods(MutableMapping, '__contains__', '__iter__', '__len__',
+            '__getitem__', '__setitem__', '__delitem__')
+
+    def test_MutableMapping_subclass(self):
+        # Test issue 9214
+        mymap = UserDict()
+        mymap['red'] = 5
+        self.assertIsInstance(mymap.keys(), Set)
+        self.assertIsInstance(mymap.keys(), KeysView)
+        self.assertIsInstance(mymap.items(), Set)
+        self.assertIsInstance(mymap.items(), ItemsView)
+
+        mymap = UserDict()
+        mymap['red'] = 5
+        z = mymap.keys() | {'orange'}
+        self.assertIsInstance(z, set)
+        list(z)
+        mymap['blue'] = 7               # Shouldn't affect 'z'
+        self.assertEqual(sorted(z), ['orange', 'red'])
+
+        mymap = UserDict()
+        mymap['red'] = 5
+        z = mymap.items() | {('orange', 3)}
+        self.assertIsInstance(z, set)
+        list(z)
+        mymap['blue'] = 7               # Shouldn't affect 'z'
+        self.assertEqual(z, {('orange', 3), ('red', 5)})
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Sequence(self):
+        for sample in [tuple, list, bytes, str]:
+            self.assertIsInstance(sample(), Sequence)
+            self.assertTrue(issubclass(sample, Sequence))
+        self.assertIsInstance(range(10), Sequence)
+        self.assertTrue(issubclass(range, Sequence))
+        self.assertIsInstance(memoryview(b""), Sequence)
+        self.assertTrue(issubclass(memoryview, Sequence))
+        self.assertTrue(issubclass(str, Sequence))
+        self.validate_abstract_methods(Sequence, '__contains__', '__iter__', '__len__',
+            '__getitem__')
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_Sequence_mixins(self):
+        class SequenceSubclass(Sequence):
+            def __init__(self, seq=()):
+                self.seq = seq
+
+            def __getitem__(self, index):
+                return self.seq[index]
+
+            def __len__(self):
+                return len(self.seq)
+
+        # Compare Sequence.index() behavior to (list|str).index() behavior
+        def assert_index_same(seq1, seq2, index_args):
+            try:
+                expected = seq1.index(*index_args)
+            except ValueError:
+                with self.assertRaises(ValueError):
+                    seq2.index(*index_args)
+            else:
+                actual = seq2.index(*index_args)
+                self.assertEqual(
+                    actual, expected, '%r.index%s' % (seq1, index_args))
+
+        for ty in list, str:
+            nativeseq = ty('abracadabra')
+            indexes = [-10000, -9999] + list(range(-3, len(nativeseq) + 3))
+            seqseq = SequenceSubclass(nativeseq)
+            for letter in set(nativeseq) | {'z'}:
+                assert_index_same(nativeseq, seqseq, (letter,))
+                for start in range(-3, len(nativeseq) + 3):
+                    assert_index_same(nativeseq, seqseq, (letter, start))
+                    for stop in range(-3, len(nativeseq) + 3):
+                        assert_index_same(
+                            nativeseq, seqseq, (letter, start, stop))
+
+    def test_ByteString(self):
+        for sample in [bytes, bytearray]:
+            self.assertIsInstance(sample(), ByteString)
+            self.assertTrue(issubclass(sample, ByteString))
+        for sample in [str, list, tuple]:
+            self.assertNotIsInstance(sample(), ByteString)
+            self.assertFalse(issubclass(sample, ByteString))
+        self.assertNotIsInstance(memoryview(b""), ByteString)
+        self.assertFalse(issubclass(memoryview, ByteString))
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_MutableSequence(self):
+        for sample in [tuple, str, bytes]:
+            self.assertNotIsInstance(sample(), MutableSequence)
+            self.assertFalse(issubclass(sample, MutableSequence))
+        for sample in [list, bytearray, deque]:
+            self.assertIsInstance(sample(), MutableSequence)
+            self.assertTrue(issubclass(sample, MutableSequence))
+        self.assertFalse(issubclass(str, MutableSequence))
+        self.validate_abstract_methods(MutableSequence, '__contains__', '__iter__',
+            '__len__', '__getitem__', '__setitem__', '__delitem__', 'insert')
+
+    def test_MutableSequence_mixins(self):
+        # Test the mixins of MutableSequence by creating a minimal concrete
+        # class inherited from it.
+        class MutableSequenceSubclass(MutableSequence):
+            def __init__(self):
+                self.lst = []
+
+            def __setitem__(self, index, value):
+                self.lst[index] = value
+
+            def __getitem__(self, index):
+                return self.lst[index]
+
+            def __len__(self):
+                return len(self.lst)
+
+            def __delitem__(self, index):
+                del self.lst[index]
+
+            def insert(self, index, value):
+                self.lst.insert(index, value)
+
+        mss = MutableSequenceSubclass()
+        mss.append(0)
+        mss.extend((1, 2, 3, 4))
+        self.assertEqual(len(mss), 5)
+        self.assertEqual(mss[3], 3)
+        mss.reverse()
+        self.assertEqual(mss[3], 1)
+        mss.pop()
+        self.assertEqual(len(mss), 4)
+        mss.remove(3)
+        self.assertEqual(len(mss), 3)
+        mss += (10, 20, 30)
+        self.assertEqual(len(mss), 6)
+        self.assertEqual(mss[-1], 30)
+        mss.clear()
+        self.assertEqual(len(mss), 0)
+
+        # issue 34427
+        # extending self should not cause infinite loop
+        items = 'ABCD'
+        mss2 = MutableSequenceSubclass()
+        mss2.extend(items + items)
+        mss.clear()
+        mss.extend(items)
+        mss.extend(mss)
+        self.assertEqual(len(mss), len(mss2))
+        self.assertEqual(list(mss), list(mss2))
+
+
+################################################################################
+### Counter
+################################################################################
+
+class CounterSubclassWithSetItem(Counter):
+    # Test a counter subclass that overrides __setitem__
+    def __init__(self, *args, **kwds):
+        self.called = False
+        Counter.__init__(self, *args, **kwds)
+    def __setitem__(self, key, value):
+        self.called = True
+        Counter.__setitem__(self, key, value)
+
+class CounterSubclassWithGet(Counter):
+    # Test a counter subclass that overrides get()
+    def __init__(self, *args, **kwds):
+        self.called = False
+        Counter.__init__(self, *args, **kwds)
+    def get(self, key, default):
+        self.called = True
+        return Counter.get(self, key, default)
+
+class TestCounter(unittest.TestCase):
+
+    def test_basics(self):
+        c = Counter('abcaba')
+        self.assertEqual(c, Counter({'a':3 , 'b': 2, 'c': 1}))
+        self.assertEqual(c, Counter(a=3, b=2, c=1))
+        self.assertIsInstance(c, dict)
+        self.assertIsInstance(c, Mapping)
+        self.assertTrue(issubclass(Counter, dict))
+        self.assertTrue(issubclass(Counter, Mapping))
+        self.assertEqual(len(c), 3)
+        self.assertEqual(sum(c.values()), 6)
+        self.assertEqual(list(c.values()), [3, 2, 1])
+        self.assertEqual(list(c.keys()), ['a', 'b', 'c'])
+        self.assertEqual(list(c), ['a', 'b', 'c'])
+        self.assertEqual(list(c.items()),
+                         [('a', 3), ('b', 2), ('c', 1)])
+        self.assertEqual(c['b'], 2)
+        self.assertEqual(c['z'], 0)
+        self.assertEqual(c.__contains__('c'), True)
+        self.assertEqual(c.__contains__('z'), False)
+        self.assertEqual(c.get('b', 10), 2)
+        self.assertEqual(c.get('z', 10), 10)
+        self.assertEqual(c, dict(a=3, b=2, c=1))
+        self.assertEqual(repr(c), "Counter({'a': 3, 'b': 2, 'c': 1})")
+        self.assertEqual(c.most_common(), [('a', 3), ('b', 2), ('c', 1)])
+        for i in range(5):
+            self.assertEqual(c.most_common(i),
+                             [('a', 3), ('b', 2), ('c', 1)][:i])
+        self.assertEqual(''.join(c.elements()), 'aaabbc')
+        c['a'] += 1         # increment an existing value
+        c['b'] -= 2         # sub existing value to zero
+        del c['c']          # remove an entry
+        del c['c']          # make sure that del doesn't raise KeyError
+        c['d'] -= 2         # sub from a missing value
+        c['e'] = -5         # directly assign a missing value
+        c['f'] += 4         # add to a missing value
+        self.assertEqual(c, dict(a=4, b=0, d=-2, e=-5, f=4))
+        self.assertEqual(''.join(c.elements()), 'aaaaffff')
+        self.assertEqual(c.pop('f'), 4)
+        self.assertNotIn('f', c)
+        for i in range(3):
+            elem, cnt = c.popitem()
+            self.assertNotIn(elem, c)
+        c.clear()
+        self.assertEqual(c, {})
+        self.assertEqual(repr(c), 'Counter()')
+        self.assertRaises(NotImplementedError, Counter.fromkeys, 'abc')
+        self.assertRaises(TypeError, hash, c)
+        c.update(dict(a=5, b=3))
+        c.update(c=1)
+        c.update(Counter('a' * 50 + 'b' * 30))
+        c.update()          # test case with no args
+        c.__init__('a' * 500 + 'b' * 300)
+        c.__init__('cdc')
+        c.__init__()
+        self.assertEqual(c, dict(a=555, b=333, c=3, d=1))
+        self.assertEqual(c.setdefault('d', 5), 1)
+        self.assertEqual(c['d'], 1)
+        self.assertEqual(c.setdefault('e', 5), 5)
+        self.assertEqual(c['e'], 5)
+
+    def test_init(self):
+        self.assertEqual(list(Counter(self=42).items()), [('self', 42)])
+        self.assertEqual(list(Counter(iterable=42).items()), [('iterable', 42)])
+        self.assertEqual(list(Counter(iterable=None).items()), [('iterable', None)])
+        self.assertRaises(TypeError, Counter, 42)
+        self.assertRaises(TypeError, Counter, (), ())
+        self.assertRaises(TypeError, Counter.__init__)
+
+    # TODO: RUSTPYTHON
+    @unittest.expectedFailure
+    def test_order_preservation(self):
+        # Input order dictates items() order
+        self.assertEqual(list(Counter('abracadabra').items()),
+               [('a', 5), ('b', 2), ('r', 2), ('c', 1), ('d', 1)])
+        # letters with same count:   ^----------^         ^---------^
+
+        # Verify retention of order even when all counts are equal
+        self.assertEqual(list(Counter('xyzpdqqdpzyx').items()),
+               [('x', 2), ('y', 2), ('z', 2), ('p', 2), ('d', 2), ('q', 2)])
+
+        # Input order dictates elements() order
+        self.assertEqual(list(Counter('abracadabra simsalabim').elements()),
+                ['a', 'a', 'a', 'a', 'a', 'a', 'a', 'b', 'b', 'b','r',
+                 'r', 'c', 'd', ' ', 's', 's', 'i', 'i', 'm', 'm', 'l'])
+
+        # Math operations order first by the order encountered in the left
+        # operand and then by the order encountered in the right operand.
+        ps = 'aaabbcdddeefggghhijjjkkl'
+        qs = 'abbcccdeefffhkkllllmmnno'
+        order = {letter: i for i, letter in enumerate(dict.fromkeys(ps + qs))}
+        def correctly_ordered(seq):
+            'Return true if the letters occur in the expected order'
+            positions = [order[letter] for letter in seq]
+            return positions == sorted(positions)
+
+        p, q = Counter(ps), Counter(qs)
+        self.assertTrue(correctly_ordered(+p))
+        self.assertTrue(correctly_ordered(-p))
+        self.assertTrue(correctly_ordered(p + q))
+        self.assertTrue(correctly_ordered(p - q))
+        self.assertTrue(correctly_ordered(p | q))
+        self.assertTrue(correctly_ordered(p & q))
+
+        p, q = Counter(ps), Counter(qs)
+        p += q
+        self.assertTrue(correctly_ordered(p))
+
+        p, q = Counter(ps), Counter(qs)
+        p -= q
+        self.assertTrue(correctly_ordered(p))
+
+        p, q = Counter(ps), Counter(qs)
+        p |= q
+        self.assertTrue(correctly_ordered(p))
+
+        p, q = Counter(ps), Counter(qs)
+        p &= q
+        self.assertTrue(correctly_ordered(p))
+
+        p, q = Counter(ps), Counter(qs)
+        p.update(q)
+        self.assertTrue(correctly_ordered(p))
+
+        p, q = Counter(ps), Counter(qs)
+        p.subtract(q)
+        self.assertTrue(correctly_ordered(p))
+
+    def test_update(self):
+        c = Counter()
+        c.update(self=42)
+        self.assertEqual(list(c.items()), [('self', 42)])
+        c = Counter()
+        c.update(iterable=42)
+        self.assertEqual(list(c.items()), [('iterable', 42)])
+        c = Counter()
+        c.update(iterable=None)
+        self.assertEqual(list(c.items()), [('iterable', None)])
+        self.assertRaises(TypeError, Counter().update, 42)
+        self.assertRaises(TypeError, Counter().update, {}, {})
+        self.assertRaises(TypeError, Counter.update)
+
+    def test_copying(self):
+        # Check that counters are copyable, deepcopyable, picklable, and
+        #have a repr/eval round-trip
+        words = Counter('which witch had which witches wrist watch'.split())
+        def check(dup):
+            msg = "\ncopy: %s\nwords: %s" % (dup, words)
+            self.assertIsNot(dup, words, msg)
+            self.assertEqual(dup, words)
+        check(words.copy())
+        check(copy.copy(words))
+        check(copy.deepcopy(words))
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            with self.subTest(proto=proto):
+                check(pickle.loads(pickle.dumps(words, proto)))
+        check(eval(repr(words)))
+        update_test = Counter()
+        update_test.update(words)
+        check(update_test)
+        check(Counter(words))
+
+    def test_copy_subclass(self):
+        class MyCounter(Counter):
+            pass
+        c = MyCounter('slartibartfast')
+        d = c.copy()
+        self.assertEqual(d, c)
+        self.assertEqual(len(d), len(c))
+        self.assertEqual(type(d), type(c))
+
+    def test_conversions(self):
+        # Convert to: set, list, dict
+        s = 'she sells sea shells by the sea shore'
+        self.assertEqual(sorted(Counter(s).elements()), sorted(s))
+        self.assertEqual(sorted(Counter(s)), sorted(set(s)))
+        self.assertEqual(dict(Counter(s)), dict(Counter(s).items()))
+        self.assertEqual(set(Counter(s)), set(s))
+
+    def test_invariant_for_the_in_operator(self):
+        c = Counter(a=10, b=-2, c=0)
+        for elem in c:
+            self.assertTrue(elem in c)
+            self.assertIn(elem, c)
+
+    def test_multiset_operations(self):
+        # Verify that adding a zero counter will strip zeros and negatives
+        c = Counter(a=10, b=-2, c=0) + Counter()
+        self.assertEqual(dict(c), dict(a=10))
+
+        elements = 'abcd'
+        for i in range(1000):
+            # test random pairs of multisets
+            p = Counter(dict((elem, randrange(-2,4)) for elem in elements))
+            p.update(e=1, f=-1, g=0)
+            q = Counter(dict((elem, randrange(-2,4)) for elem in elements))
+            q.update(h=1, i=-1, j=0)
+            for counterop, numberop in [
+                (Counter.__add__, lambda x, y: max(0, x+y)),
+                (Counter.__sub__, lambda x, y: max(0, x-y)),
+                (Counter.__or__, lambda x, y: max(0,x,y)),
+                (Counter.__and__, lambda x, y: max(0, min(x,y))),
+            ]:
+                result = counterop(p, q)
+                for x in elements:
+                    self.assertEqual(numberop(p[x], q[x]), result[x],
+                                     (counterop, x, p, q))
+                # verify that results exclude non-positive counts
+                self.assertTrue(x>0 for x in result.values())
+
+        elements = 'abcdef'
+        for i in range(100):
+            # verify that random multisets with no repeats are exactly like sets
+            p = Counter(dict((elem, randrange(0, 2)) for elem in elements))
+            q = Counter(dict((elem, randrange(0, 2)) for elem in elements))
+            for counterop, setop in [
+                (Counter.__sub__, set.__sub__),
+                (Counter.__or__, set.__or__),
+                (Counter.__and__, set.__and__),
+            ]:
+                counter_result = counterop(p, q)
+                set_result = setop(set(p.elements()), set(q.elements()))
+                self.assertEqual(counter_result, dict.fromkeys(set_result, 1))
+
+    def test_inplace_operations(self):
+        elements = 'abcd'
+        for i in range(1000):
+            # test random pairs of multisets
+            p = Counter(dict((elem, randrange(-2,4)) for elem in elements))
+            p.update(e=1, f=-1, g=0)
+            q = Counter(dict((elem, randrange(-2,4)) for elem in elements))
+            q.update(h=1, i=-1, j=0)
+            for inplace_op, regular_op in [
+                (Counter.__iadd__, Counter.__add__),
+                (Counter.__isub__, Counter.__sub__),
+                (Counter.__ior__, Counter.__or__),
+                (Counter.__iand__, Counter.__and__),
+            ]:
+                c = p.copy()
+                c_id = id(c)
+                regular_result = regular_op(c, q)
+                inplace_result = inplace_op(c, q)
+                self.assertEqual(inplace_result, regular_result)
+                self.assertEqual(id(inplace_result), c_id)
+
+    def test_subtract(self):
+        c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
+        c.subtract(a=1, b=2, c=-3, d=10, e=20, f=30, h=-50)
+        self.assertEqual(c, Counter(a=-6, b=-2, c=8, d=0, e=-5, f=-30, g=40, h=50))
+        c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
+        c.subtract(Counter(a=1, b=2, c=-3, d=10, e=20, f=30, h=-50))
+        self.assertEqual(c, Counter(a=-6, b=-2, c=8, d=0, e=-5, f=-30, g=40, h=50))
+        c = Counter('aaabbcd')
+        c.subtract('aaaabbcce')
+        self.assertEqual(c, Counter(a=-1, b=0, c=-1, d=1, e=-1))
+
+        c = Counter()
+        c.subtract(self=42)
+        self.assertEqual(list(c.items()), [('self', -42)])
+        c = Counter()
+        c.subtract(iterable=42)
+        self.assertEqual(list(c.items()), [('iterable', -42)])
+        self.assertRaises(TypeError, Counter().subtract, 42)
+        self.assertRaises(TypeError, Counter().subtract, {}, {})
+        self.assertRaises(TypeError, Counter.subtract)
+
+    def test_unary(self):
+        c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
+        self.assertEqual(dict(+c), dict(c=5, d=10, e=15, g=40))
+        self.assertEqual(dict(-c), dict(a=5))
+
+    def test_repr_nonsortable(self):
+        c = Counter(a=2, b=None)
+        r = repr(c)
+        self.assertIn("'a': 2", r)
+        self.assertIn("'b': None", r)
+
+    def test_helper_function(self):
+        # two paths, one for real dicts and one for other mappings
+        elems = list('abracadabra')
+
+        d = dict()
+        _count_elements(d, elems)
+        self.assertEqual(d, {'a': 5, 'r': 2, 'b': 2, 'c': 1, 'd': 1})
+
+        m = OrderedDict()
+        _count_elements(m, elems)
+        self.assertEqual(m,
+             OrderedDict([('a', 5), ('b', 2), ('r', 2), ('c', 1), ('d', 1)]))
+
+        # test fidelity to the pure python version
+        c = CounterSubclassWithSetItem('abracadabra')
+        self.assertTrue(c.called)
+        self.assertEqual(dict(c), {'a': 5, 'b': 2, 'c': 1, 'd': 1, 'r':2 })
+        c = CounterSubclassWithGet('abracadabra')
+        self.assertTrue(c.called)
+        self.assertEqual(dict(c), {'a': 5, 'b': 2, 'c': 1, 'd': 1, 'r':2 })
+
+
+################################################################################
+### Run tests
+################################################################################
+
+def test_main(verbose=None):
+    # TODO: RUSTPYTHON
+    # NamedTupleDocs = doctest.DocTestSuite(module=collections)
+    # test_classes = [TestNamedTuple, NamedTupleDocs, TestOneTrickPonyABCs,
+    test_classes = [TestNamedTuple, TestOneTrickPonyABCs,
+                    TestCollectionABCs, TestCounter, TestChainMap,
+                    TestUserObjects,
+                    ]
+    support.run_unittest(*test_classes)
+    # TODO: RUSTPYTHON
+    # support.run_doctest(collections, verbose)
+
+
+if __name__ == "__main__":
+    test_main(verbose=True)