bpo-38093: Correctly returns AsyncMock for async subclasses. (GH-15947)

Lib/unittest/test/testmock/testasync.py

@@ -382,35 +382,88 @@ class AsyncArguments(unittest.TestCase):
 class AsyncContextManagerTest(unittest.TestCase):
 
     class WithAsyncContextManager:
-
         async def __aenter__(self, *args, **kwargs):
             return self
 
         async def __aexit__(self, *args, **kwargs):
             pass
 
-    def test_magic_methods_are_async_mocks(self):
-        mock = MagicMock(self.WithAsyncContextManager())
-        self.assertIsInstance(mock.__aenter__, AsyncMock)
-        self.assertIsInstance(mock.__aexit__, AsyncMock)
+    class WithSyncContextManager:
+        def __enter__(self, *args, **kwargs):
+            return self
+
+        def __exit__(self, *args, **kwargs):
+            pass
+
+    class ProductionCode:
+        # Example real-world(ish) code
+        def __init__(self):
+            self.session = None
+
+        async def main(self):
+            async with self.session.post('https://python.org') as response:
+                val = await response.json()
+                return val
+
+    def test_async_magic_methods_are_async_mocks_with_magicmock(self):
+        cm_mock = MagicMock(self.WithAsyncContextManager())
+        self.assertIsInstance(cm_mock.__aenter__, AsyncMock)
+        self.assertIsInstance(cm_mock.__aexit__, AsyncMock)
+
+    def test_magicmock_has_async_magic_methods(self):
+        cm = MagicMock(name='magic_cm')
+        self.assertTrue(hasattr(cm, "__aenter__"))
+        self.assertTrue(hasattr(cm, "__aexit__"))
+
+    def test_magic_methods_are_async_functions(self):
+        cm = MagicMock(name='magic_cm')
+        self.assertIsInstance(cm.__aenter__, AsyncMock)
+        self.assertIsInstance(cm.__aexit__, AsyncMock)
+        # AsyncMocks are also coroutine functions
+        self.assertTrue(asyncio.iscoroutinefunction(cm.__aenter__))
+        self.assertTrue(asyncio.iscoroutinefunction(cm.__aexit__))
+
+    def test_set_return_value_of_aenter(self):
+        def inner_test(mock_type):
+            pc = self.ProductionCode()
+            pc.session = MagicMock(name='sessionmock')
+            cm = mock_type(name='magic_cm')
+            response = AsyncMock(name='response')
+            response.json = AsyncMock(return_value={'json': 123})
+            cm.__aenter__.return_value = response
+            pc.session.post.return_value = cm
+            result = asyncio.run(pc.main())
+            self.assertEqual(result, {'json': 123})
+
+        for mock_type in [AsyncMock, MagicMock]:
+            with self.subTest(f"test set return value of aenter with {mock_type}"):
+                inner_test(mock_type)
 
     def test_mock_supports_async_context_manager(self):
-        called = False
-        instance = self.WithAsyncContextManager()
-        mock_instance = MagicMock(instance)
+        def inner_test(mock_type):
+            called = False
+            cm = self.WithAsyncContextManager()
+            cm_mock = mock_type(cm)
 
-        async def use_context_manager():
-            nonlocal called
-            async with mock_instance as result:
-                called = True
-            return result
+            async def use_context_manager():
+                nonlocal called
+                async with cm_mock as result:
+                    called = True
+                return result
+
+            cm_result = asyncio.run(use_context_manager())
+            self.assertTrue(called)
+            self.assertTrue(cm_mock.__aenter__.called)
+            self.assertTrue(cm_mock.__aexit__.called)
+            cm_mock.__aenter__.assert_awaited()
+            cm_mock.__aexit__.assert_awaited()
+            # We mock __aenter__ so it does not return self
+            self.assertIsNot(cm_mock, cm_result)
+
+        for mock_type in [AsyncMock, MagicMock]:
+            with self.subTest(f"test context manager magics with {mock_type}"):
+                inner_test(mock_type)
 
-        result = asyncio.run(use_context_manager())
-        self.assertTrue(called)
-        self.assertTrue(mock_instance.__aenter__.called)
-        self.assertTrue(mock_instance.__aexit__.called)
-        self.assertIsNot(mock_instance, result)
-        self.assertIsInstance(result, AsyncMock)
 
     def test_mock_customize_async_context_manager(self):
         instance = self.WithAsyncContextManager()
@@ -478,27 +531,30 @@ class AsyncIteratorTest(unittest.TestCase):
 
             raise StopAsyncIteration
 
-    def test_mock_aiter_and_anext(self):
-        instance = self.WithAsyncIterator()
-        mock_instance = MagicMock(instance)
+    def test_aiter_set_return_value(self):
+        mock_iter = AsyncMock(name="tester")
+        mock_iter.__aiter__.return_value = [1, 2, 3]
+        async def main():
+            return [i async for i in mock_iter]
+        result = asyncio.run(main())
+        self.assertEqual(result, [1, 2, 3])
 
-        self.assertEqual(asyncio.iscoroutine(instance.__aiter__),
-                         asyncio.iscoroutine(mock_instance.__aiter__))
-        self.assertEqual(asyncio.iscoroutine(instance.__anext__),
-                         asyncio.iscoroutine(mock_instance.__anext__))
+    def test_mock_aiter_and_anext_asyncmock(self):
+        def inner_test(mock_type):
+            instance = self.WithAsyncIterator()
+            mock_instance = mock_type(instance)
+            # Check that the mock and the real thing bahave the same
+            # __aiter__ is not actually async, so not a coroutinefunction
+            self.assertFalse(asyncio.iscoroutinefunction(instance.__aiter__))
+            self.assertFalse(asyncio.iscoroutinefunction(mock_instance.__aiter__))
+            # __anext__ is async
+            self.assertTrue(asyncio.iscoroutinefunction(instance.__anext__))
+            self.assertTrue(asyncio.iscoroutinefunction(mock_instance.__anext__))
 
-        iterator = instance.__aiter__()
-        if asyncio.iscoroutine(iterator):
-            iterator = asyncio.run(iterator)
+        for mock_type in [AsyncMock, MagicMock]:
+            with self.subTest(f"test aiter and anext corourtine with {mock_type}"):
+                inner_test(mock_type)
 
-        mock_iterator = mock_instance.__aiter__()
-        if asyncio.iscoroutine(mock_iterator):
-            mock_iterator = asyncio.run(mock_iterator)
-
-        self.assertEqual(asyncio.iscoroutine(iterator.__aiter__),
-                         asyncio.iscoroutine(mock_iterator.__aiter__))
-        self.assertEqual(asyncio.iscoroutine(iterator.__anext__),
-                         asyncio.iscoroutine(mock_iterator.__anext__))
 
     def test_mock_async_for(self):
         async def iterate(iterator):
@@ -509,19 +565,30 @@ class AsyncIteratorTest(unittest.TestCase):
             return accumulator
 
         expected = ["FOO", "BAR", "BAZ"]
-        with self.subTest("iterate through default value"):
-            mock_instance = MagicMock(self.WithAsyncIterator())
-            self.assertEqual([], asyncio.run(iterate(mock_instance)))
+        def test_default(mock_type):
+            mock_instance = mock_type(self.WithAsyncIterator())
+            self.assertEqual(asyncio.run(iterate(mock_instance)), [])
 
-        with self.subTest("iterate through set return_value"):
-            mock_instance = MagicMock(self.WithAsyncIterator())
+
+        def test_set_return_value(mock_type):
+            mock_instance = mock_type(self.WithAsyncIterator())
             mock_instance.__aiter__.return_value = expected[:]
-            self.assertEqual(expected, asyncio.run(iterate(mock_instance)))
+            self.assertEqual(asyncio.run(iterate(mock_instance)), expected)
 
-        with self.subTest("iterate through set return_value iterator"):
-            mock_instance = MagicMock(self.WithAsyncIterator())
+        def test_set_return_value_iter(mock_type):
+            mock_instance = mock_type(self.WithAsyncIterator())
             mock_instance.__aiter__.return_value = iter(expected[:])
-            self.assertEqual(expected, asyncio.run(iterate(mock_instance)))
+            self.assertEqual(asyncio.run(iterate(mock_instance)), expected)
+
+        for mock_type in [AsyncMock, MagicMock]:
+            with self.subTest(f"default value with {mock_type}"):
+                test_default(mock_type)
+
+            with self.subTest(f"set return_value with {mock_type}"):
+                test_set_return_value(mock_type)
+
+            with self.subTest(f"set return_value iterator with {mock_type}"):
+                test_set_return_value_iter(mock_type)
 
 
 class AsyncMockAssert(unittest.TestCase):