Cleaning up pending tasks

[matthew-at-qamcom]

I'm extremely new to asyncio, so my apologies if this is obvious. If I've made an error, I'd love an explanation.

I was receiving the error Task was destroyed but it is pending!, even though all my tests were passing. My tests were basically (1) create web service (2) test API functionality using aiohttp, for example:

@pytest.mark.asyncio
async def test_server_running(event_loop, unused_tcp_port):
    port = unused_tcp_port
    make_service(port) # Creates a Tornado Application

    async with aiohttp.ClientSession() as session:
        async with session.get(f"http://localhost:{port}") as response:
            result = await response.text()
            assert result is not None

    # await tear_down(event_loop) # <-- see below

I was able to resolve this with a tear down function (inspired by the method AsyncTestCase.tearDown().

async def tear_down(event_loop):
    # Collect all tasks and cancel those that are not 'done'.                                       
    tasks = asyncio.all_tasks(event_loop)
    tasks = [t for t in tasks if not t.done()]
    for task in tasks:
        task.cancel()

    # Wait for all tasks to complete, ignoring any CancelledErrors                                  
    try:
        await asyncio.wait(tasks)
    except asyncio.exceptions.CancelledError:
        pass

Is this an appropriate solution to the Task was destroyed but it is pending! error? Did I miss something obvious? Is there a better way?

Thanks.

[matthew-at-qamcom]

This issue feels similar to #200 and #309.

[seifertm]

This is certainly not obvious and your question is very valid.

At the moment, there's no "official" way to clean up tasks after a test finishes. Your approach seems to be a reasonable workaround for now.

I'll mark this as a duplicate of #200.

[matthew-at-qamcom]

Thanks for your response. It's greatly appreciated.