使用 @pytest.fixture(scope="module") 和 @pytest.mark.asyncio

Question

I think the example below is a really common use case:

1. create a connection to a database once ,
2. pass this connection around to test which insert data
3. pass the connection to a test which verifies the data.

Changing the scope of @pytest.fixture(scope="module") causes ScopeMismatch: You tried to access the 'function' scoped fixture 'event_loop' with a 'module' scoped request object, involved factories .

Also, the test_insert and test_find coroutine do not need the event_loop argument because the loop is accessible already by passing the connection.

Any ideas how to fix those two issues?

import pytest

@pytest.fixture(scope="function")  # <-- want this to be scope="module"; run once!
@pytest.mark.asyncio
async def connection(event_loop):
    """ Expensive function; want to do in the module scope. Only this function needs `event_loop`!
    """
    conn await = make_connection(event_loop)
    return conn


@pytest.mark.dependency()
@pytest.mark.asyncio
async def test_insert(connection, event_loop):  # <-- does not need event_loop arg
    """ Test insert into database.

        NB does not need event_loop argument; just the connection.
    """
    _id = 0
    success = await connection.insert(_id, "data")
    assert success == True


@pytest.mark.dependency(depends=['test_insert'])
@pytest.mark.asyncio
async def test_find(connection, event_loop):  # <-- does not need event_loop arg
    """ Test database find.

        NB does not need event_loop argument; just the connection.
    """
    _id = 0
    data = await connection.find(_id)
    assert data == "data"

Answer 1

The solution is to redefine the event_loop fixture with the module scope. Include that in the test file.

@pytest.fixture(scope="module")
def event_loop():
    loop = asyncio.get_event_loop()
    yield loop
    loop.close()

Answer 2

Similar ScopeMismatch issue was raised in github for pytest-asyncio ( link ). The solution (below) works for me:

@pytest.yield_fixture(scope='class')
def event_loop(request):
    loop = asyncio.get_event_loop_policy().new_event_loop()
    yield loop
    loop.close()