diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 37ea5c7..9e69298 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -1042,8 +1042,7 @@
     the left."""
     def __contains__(self, item):
         for _call in self:
-            if len(item) != len(_call):
-                continue
+            assert len(item) == len(_call)
             if all([
                 expected == actual
                 for expected, actual in zip(item, _call)
@@ -1856,7 +1855,8 @@
 
     def __exit__(self, *args):
         """Unpatch the dict."""
-        self._unpatch_dict()
+        if self._original is not None:
+            self._unpatch_dict()
         return False
 
 
@@ -2168,7 +2168,7 @@
         self.__dict__['__code__'] = code_mock
 
     async def _execute_mock_call(self, /, *args, **kwargs):
-        # This is nearly just like super(), except for sepcial handling
+        # This is nearly just like super(), except for special handling
         # of coroutines
 
         _call = self.call_args
@@ -2541,12 +2541,6 @@
         return tuple.__getattribute__(self, attr)
 
 
-    def count(self, /, *args, **kwargs):
-        return self.__getattr__('count')(*args, **kwargs)
-
-    def index(self, /, *args, **kwargs):
-        return self.__getattr__('index')(*args, **kwargs)
-
     def _get_call_arguments(self):
         if len(self) == 2:
             args, kwargs = self
@@ -2917,9 +2911,6 @@
         code_mock.co_flags = inspect.CO_ITERABLE_COROUTINE
         self.__dict__['__code__'] = code_mock
 
-    def __aiter__(self):
-        return self
-
     async def __anext__(self):
         try:
             return next(self.iterator)
diff --git a/Lib/unittest/test/testmock/testasync.py b/Lib/unittest/test/testmock/testasync.py
index 992076d..bf93622 100644
--- a/Lib/unittest/test/testmock/testasync.py
+++ b/Lib/unittest/test/testmock/testasync.py
@@ -16,38 +16,28 @@
 
 
 class AsyncClass:
-    def __init__(self):
-        pass
-    async def async_method(self):
-        pass
-    def normal_method(self):
-        pass
+    def __init__(self): pass
+    async def async_method(self): pass
+    def normal_method(self): pass
 
     @classmethod
-    async def async_class_method(cls):
-        pass
+    async def async_class_method(cls): pass
 
     @staticmethod
-    async def async_static_method():
-        pass
+    async def async_static_method(): pass
 
 
 class AwaitableClass:
-    def __await__(self):
-        yield
+    def __await__(self): yield
 
-async def async_func():
-    pass
+async def async_func(): pass
 
-async def async_func_args(a, b, *, c):
-    pass
+async def async_func_args(a, b, *, c): pass
 
-def normal_func():
-    pass
+def normal_func(): pass
 
 class NormalClass(object):
-    def a(self):
-        pass
+    def a(self): pass
 
 
 async_foo_name = f'{__name__}.AsyncClass'
@@ -402,8 +392,7 @@
 
 class AsyncArguments(IsolatedAsyncioTestCase):
     async def test_add_return_value(self):
-        async def addition(self, var):
-            return var + 1
+        async def addition(self, var): pass
 
         mock = AsyncMock(addition, return_value=10)
         output = await mock(5)
@@ -411,8 +400,7 @@
         self.assertEqual(output, 10)
 
     async def test_add_side_effect_exception(self):
-        async def addition(var):
-            return var + 1
+        async def addition(var): pass
         mock = AsyncMock(addition, side_effect=Exception('err'))
         with self.assertRaises(Exception):
             await mock(5)
@@ -553,18 +541,14 @@
 class AsyncContextManagerTest(unittest.TestCase):
 
     class WithAsyncContextManager:
-        async def __aenter__(self, *args, **kwargs):
-            return self
+        async def __aenter__(self, *args, **kwargs): pass
 
-        async def __aexit__(self, *args, **kwargs):
-            pass
+        async def __aexit__(self, *args, **kwargs): pass
 
     class WithSyncContextManager:
-        def __enter__(self, *args, **kwargs):
-            return self
+        def __enter__(self, *args, **kwargs): pass
 
-        def __exit__(self, *args, **kwargs):
-            pass
+        def __exit__(self, *args, **kwargs): pass
 
     class ProductionCode:
         # Example real-world(ish) code
@@ -673,16 +657,9 @@
         def __init__(self):
             self.items = ["foo", "NormalFoo", "baz"]
 
-        def __aiter__(self):
-            return self
+        def __aiter__(self): pass
 
-        async def __anext__(self):
-            try:
-                return self.items.pop()
-            except IndexError:
-                pass
-
-            raise StopAsyncIteration
+        async def __anext__(self): pass
 
     def test_aiter_set_return_value(self):
         mock_iter = AsyncMock(name="tester")
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 6773467..9b9e066 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1868,6 +1868,11 @@
         with self.assertRaises(StopIteration):
             next(f1)
 
+    def test_mock_open_next_with_readline_with_return_value(self):
+        mopen = mock.mock_open(read_data='foo\nbarn')
+        mopen.return_value.readline.return_value = 'abc'
+        self.assertEqual('abc', next(mopen()))
+
     def test_mock_open_write(self):
         # Test exception in file writing write()
         mock_namedtemp = mock.mock_open(mock.MagicMock(name='JLV'))
diff --git a/Lib/unittest/test/testmock/testpatch.py b/Lib/unittest/test/testmock/testpatch.py
index 438dfd8..f1bc0e1 100644
--- a/Lib/unittest/test/testmock/testpatch.py
+++ b/Lib/unittest/test/testmock/testpatch.py
@@ -770,6 +770,14 @@
         self.assertEqual(d, original)
 
 
+    def test_patch_dict_stop_without_start(self):
+        d = {'foo': 'bar'}
+        original = d.copy()
+        patcher = patch.dict(d, [('spam', 'eggs')], clear=True)
+        self.assertEqual(patcher.stop(), False)
+        self.assertEqual(d, original)
+
+
     def test_patch_dict_class_decorator(self):
         this = self
         d = {'spam': 'eggs'}