如何修补异步类方法？

Question

我正在处理以下问题，我有一个类，我想模拟其补丁的异步方法：

class ExampleClass:

    async def asy_method(self, param):

        return await some_coroutine(self, param)

example_instance = ExampleClass()

我只想打补丁

await example_instance.asy_method('test_param')

通常我会用

mocker.patch('ExampleClass.asy_method', new_callable=AsyncMock)

其中，mocker是pytest-mock插件的固定装置，而AsyncMock具有以下形式

class AsyncMock(mock.MagicMock):

    async def __call__(self, *args, **kwargs):

         return super(AsyncMock, self).__call__(*args, **kwargs)

这会给我一个Mock对象，它在调用时的行为像协程。问题是，我想访问self传递给方法的属性。self仅在您进行设置的情况下才传递给模拟对象 autospec=True（另请参阅Python Doc，了解如何修补未绑定的方法），您不能与一起使用new_callable。

有谁知道如何解决这个问题？

Answer 1

确实，您不能混合使用自动指定和新的可调用项。相反，可以自动指定方法，然后替换side_effect属性，并为其指定一个AsyncMock()实例：from unittest import mockdef configure_coroutine_mock(mock_function, klass=AsyncMock):&nbsp; &nbsp; """Make an autospecced async function return a coroutine mock"""&nbsp; &nbsp; mock_function.side_effect = AsyncMock()&nbsp; &nbsp; # mark the side effect as a child of the original mock object&nbsp; &nbsp; # so transitive access is recorded on the parent mock too. This is&nbsp;&nbsp; &nbsp; # what .return_value does normally&nbsp; &nbsp; mock._check_and_set_parent(&nbsp; &nbsp; &nbsp; &nbsp; mock_function.mock, mock_function.side_effect,&nbsp; &nbsp; &nbsp; &nbsp; None, '()')&nbsp; &nbsp; return mock_asy_method.side_effectwith mocker.patch('ExampleClass.asy_method', autospec=True) as mock_asy_method:&nbsp; &nbsp; configure_coroutine_mock(mock_asy_method)因为AsyncMock()是可调用的对象，所以每次mock_asy_method调用都会调用，并将参数传递给该对象。然后，该调用的结果用于从返回mock_asy_method()：>>> from unittest import mock>>> class ExampleClass:...&nbsp; &nbsp; &nbsp;async def asy_method(self, param):...&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;return await some_coroutine(self, param)...>>> example_instance = ExampleClass()>>> with mock.patch('__main__.ExampleClass.asy_method', autospec=True) as mock_asy_method:...&nbsp; &nbsp; &nbsp;configure_coroutine_mock(mock_asy_method)...&nbsp; &nbsp; &nbsp;print(example_instance.asy_method('foo'))&nbsp; # call to patched class coroutine...&nbsp; &nbsp; &nbsp;print(mock_asy_method.mock_calls)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; # calls are recorded...<AsyncMock name='asy_method()' id='4563887496'><coroutine object AsyncMock.__call__ at 0x1100780f8>[call(<__main__.ExampleClass object at 0x10ffac1d0>, 'foo')]如您所见，self参数和参数记录在调用中，因为这mock_asy_method是一种适当的函数。当然，只有在AsyncMock()实际等待返回的呼叫结果时，我们才会看到该呼叫也被记录：>>> with mock.patch('__main__.ExampleClass.asy_method', autospec=True) as mock_asy_method:...&nbsp; &nbsp; &nbsp;configure_coroutine_mock(mock_asy_method)...&nbsp; &nbsp; &nbsp;loop = asyncio.get_event_loop()...&nbsp; &nbsp; &nbsp;coro = example_instance.asy_method('foo')...&nbsp; &nbsp; &nbsp;loop.run_until_complete(coro)...&nbsp; &nbsp; &nbsp;print(mock_asy_method.mock_calls)...&nbsp; &nbsp; &nbsp;<AsyncMock name='asy_method()' id='4564408920'><AsyncMock name='asy_method()()' id='4564999360'>&nbsp; &nbsp;&nbsp;[call(<__main__.ExampleClass object at 0x10ffac1d0>, 'foo'),&nbsp;call()(<__main__.ExampleClass object at 0x10ffac1d0>, 'foo')]