"Event Loop is Closed" During Tests

[rgajason]

Hello all,

I'm running into a scenario using the test client where asyncio is raising "event loop is closed". I'm trying to narrow it down into a minimal example, but haven't gotten there yet. In the meantime, I'm hoping someone has ran into a similar issue and can share their experience to at least help me narrow down the issue.

Some details:

• I'm using the AsyncTestClient now, but was previously using the TestClient and getting the same results
• The tests that fail use a "real" MongoDB instance. The mock client (from mongomock_motor) doesn't work for some of my tests because it doesn't support List[Link[...]].
• I'm using Beanie
• Each test prepares the database by using the test client to insert data into the DB via a POST endpoint (vs inserting data directly)

The tests that only use mongomock_motor without my hacks to connect to real Mongo and initialize Beanie work.

Here's a sample stack trace when using the "real" DB:

Traceback (most recent call last):
  File "/myapp/.venv/lib/python3.10/site-packages/starlite/middleware/exceptions/middleware.py", line 47, in __call__
    await self.app(scope, receive, send)
  File "/myapp/.venv/lib/python3.10/site-packages/starlite/routes/http.py", line 79, in handle
    response = await self._get_response_for_request(
  File "/myapp/.venv/lib/python3.10/site-packages/starlite/routes/http.py", line 131, in _get_response_for_request
    response = await self._call_handler_function(
  File "/myapp/.venv/lib/python3.10/site-packages/starlite/routes/http.py", line 160, in _call_handler_function
    response_data, cleanup_group = await self._get_response_data(
  File "/myapp/.venv/lib/python3.10/site-packages/starlite/routes/http.py", line 218, in _get_response_data
    data = await route_handler.fn.value(**parsed_kwargs)
  File "/myapp/inventory/github/controllers.py", line 221, in create_organization
    await data.create()
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/documents.py", line 248, in create
    return await self.insert(session=session)
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/actions.py", line 221, in wrapper
    result = await f(self, *args, skip_actions=skip_actions, **kwargs)
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/utils/state.py", line 39, in wrapper
    result = await f(self, *args, **kwargs)
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/utils/state.py", line 49, in wrapper
    result = await f(self, *args, **kwargs)
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/utils/self_validation.py", line 12, in wrapper
    return await f(self, *args, **kwargs)
  File "/myapp/.venv/lib/python3.10/site-packages/beanie/odm/documents.py", line 231, in insert
    result = await self.get_motor_collection().insert_one(
  File "/myapp/.venv/lib/python3.10/site-packages/motor/metaprogramming.py", line 73, in method
    return framework.run_on_executor(
  File "/myapp/.venv/lib/python3.10/site-packages/motor/frameworks/asyncio/__init__.py", line 74, in run_on_executor
    return loop.run_in_executor(_EXECUTOR, functools.partial(fn, *args, **kwargs))
  File "/usr/local/Cellar/python@3.10/3.10.9/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/base_events.py", line 808, in run_in_executor
    self._check_closed()
  File "/usr/local/Cellar/python@3.10/3.10.9/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/base_events.py", line 515, in _check_closed
    raise RuntimeError('Event loop is closed')

One thing that has been bothering me - regardless of using a mock or real DB, my test client fixture doesn't appear to run the on_startup hooks:

import pytest
from starlite.testing import AsyncTestClient

from myapp.main import app


@pytest.fixture()
def test_client() -> AsyncTestClient:
    return AsyncTestClient(app=app)

I have to to include an additional fixture:

@pytest.fixture()
def mongo_client() -> AsyncMongoMockClient:
    client = AsyncMongoMockClient()
    asyncio.run(
        init_beanie(
            database=client.myapp_pytest,
            document_models=[Widget, Myother, Modelshere],
        )
    )
    return client

...and then ensure it is referenced in data fixtures (or enable autouse):

@pytest.fixture()
def widget(mongo_client: AsyncMongoMockClient) -> Widget:
    return WidgetFactory.build()

I'm sorry, I know this post is all over the place. I'm at a loss for narrowing all of this down. I'm guessing that there is some issue with competing lifecycle managers.

Thanks for your time and any direction that can be offered.

[provinzkraut]

Can you provide a reproducible example or at least include the code of the test that causes this error?

Also, how are you using the test_client fixture? The fact that it’s not running the lifecycle hooks tells me there might be something wrong about that.

[provinzkraut]

You need to use the AsyncTestClient instance as an async context manager.

[rgajason]

Sorry if I'm being dense... I tried modifying test_read_parent_by_id() to:

@pytest.mark.asyncio()
async def test_read_parent_by_id(test_client: AsyncTestClient, parent: Parent):
    async with test_client as client:
        pdb = await prepare_one_parent(test_client=client, parent=parent)

        r = await client.get(f"/sandbox/parent/{pdb['id']}")
        r.raise_for_status()
        assert r.status_code == HTTP_200_OK

        p = parent_from_dict(r.json())
        assert p == parent

(all other code the same)

I get the same results - if I remove the mongo_client() fixture, remove autouse, or remove the init_beanie() call the tests fail with beanie.exceptions.CollectionWasNotInitialized.

I noticed that in the Starlite docs the async examples aren't using the pytest.mark.asyncio() decorator and test functions are sync, but I'm thinking that is a copy/paste issue since async with isn't valid inside of a sync function.

[rgajason]

I think I have some new/better information based on comparing your advice with the tests in Beanie's code. I'll do further testing and report back. Thanks for the guidance thus far.

[provinzkraut]

I noticed that in the Starlite docs the async examples aren't using the pytest.mark.asyncio()

You can set asyncio_mode = "auto" so you won't need this.

and test functions are sync, but I'm thinking that is a copy/paste issue since async with isn't valid inside of a sync function.

That's correct, the documentation is wrong there. I created an issue: #1099

[rgajason]

Sorry for the huge delay in getting back. Short story is, secret sauce is what @provinzkraut was mentioning regarding the context manager:

@pytest.fixture()
async def test_client() -> AsyncTestClient:
    async with AsyncTestClient(app=app) as client:
        yield client

(and setting asyncio_mode to auto in pytest configuration)

Once I did that, the "event loop is closed" error went away and the startup hooks ran as expected.

Thank you!