Python - object MagicMock can't be used in 'await' expression

Question

When I was trying to mock an async function in unittest with MagicMock, I got this exception:

TypeError: object MagicMock can\'t be used in \'await\' expr

Answer 1

I found this comment very useful when trying to await a mock object in Python < 3.8. You simply create a child class AsyncMock that inherits from MagicMock and overwrites a __call__ method to be a coroutine:

class AsyncMock(MagicMock):
    async def __call__(self, *args, **kwargs):
        return super(AsyncMock, self).__call__(*args, **kwargs)

Then, inside your test, do:

@pytest.mark.asyncio
async def test_my_method():
    # Test "my_method" coroutine by injecting an async mock
    my_mock = AsyncMock()
    assert await my_method(my_mock)

you might also want to install pytest-asyncio