Full control over awaitable mock

[Kentzo]

When writing asyncio tests it is to control when and what awaitable mock should return.

Here is an example to give an idea:

class MagicCoro(unittest.mock.Mock):
    """
    >>> m = unittest.mock.MagicMock()
    >>> m.coro = MagicCoro(return_value=42)
    >>> assert await m.coro() == 42
    >>> assert m.exit.is_set()
    """
    def __init__(self, run_event=None, return_value=None):
        async def coro(*args, **kwargs):
            self.enter.set()

            if self.run:
                await self.run.wait()

            self.exit.set()

            return self.value

        super().__init__(wraps=coro)

        self.enter = asyncio.Event()
        self.run = run_event
        self.exit = asyncio.Event()
        self.value = return_value

    def _get_child_mock(self, **kw):
        return unittest.mock.MagicMock(**kw)

This allows to:

• provide a return value
• provide an event to wait for allowing user to control completion order
• assert whether coroutine was entered or exited

[Martiusweb]

This is something that can be added to the helpers module:
http://asynctest.readthedocs.io/en/latest/asynctest.helpers.html

[Kentzo]

@Martiusweb I was thinking about adding an extra attribute to CoroutineMock to "await" its call:

class AsyncContext:
    async def __aenter__(self):
        pass
    async def __aexit__(self, *args):
        pass

def test():
    m = asynctest.MagicMock(spec=AsyncContext)
    f1 = asyncio.ensure_future(some_async_method(m))
    await m.__aenter__._mock_async_wait()  # wait till some_async_method will enter the context