Concurrent async fixture setup / teardown

This is more an idea / question how hard it would be.

While pytest ensures stable fixture order, it's made with synchronous fixtures in mind.

pytest-asyncio on the other hand allows for async fixtures and typically async test cases imply async code under test which implies async dependencies which imply async fixtures.

Thus, how about running setup and teardown asynchronously too, for example:

@pytest.fixture
async def A():
    ...
    yield
    ...

@pytest.fixture
async def B(A):
    ...
    yield
    ...

@pytest.fixture
async def C(A):
    ...
    yield
    ...

@pytest.fixture
async def D(B, C):
    ...
    yield
    ...

Would run as:

• A setup
• asyncio.gather(B setup, C setup)
• D setup
• test case
• D teardown
• asyncio.gather(B teardown, C teardown)
• A teardown

Start by reviewing the issue's async fixture dependency example and how pytest currently orders fixture setup and teardown. Determine whether concurrent setup and teardown can preserve dependency ordering and cleanup guarantees. Done means the supported behavior and scope are defined, with tests covering the proposed execution order.