Is there a good way to use multiple TestClient instances?

[tomkcook]

I have a web application with several user roles. I've been testing it using httpx, with a different pytest fixture for each role:

@pytest.fixture
def admin_client(test_url, admin_token):
    return httpx.Client(test_url, headers={"Authorization": f"Bearer {admin_token}"})

@pytest.fixture
def user_client(test_url, user_token):
    return httpx.Client(test_url, headers={"Authorization": f"Bearer {user_token}"})

I'm now trying to change my tests to use the starlette TestClient so that I can generate full test coverage statistics. Changing the code above to use TestClient naively causes problems:

from app.main import app

@pytest.fixture
async def admin_client(test_url, admin_token):
    return TestClient(app, headers={"Authorization": f"Bearer {admin_token}"})

@pytest.fixture
async def user_client(test_url, user_token):
    return TestClient(app, headers={"Authorization": f"Bearer {user_token}"})

If I use these in the wrong order, I get exceptions of this variety:

E           RuntimeError: Task <Task pending name='starlette.middleware.base.BaseHTTPMiddleware.__call__.<locals>.call_next.<locals>.coro' coro=<BaseHTTPMiddleware.__call__.<locals>.call_next.<locals>.coro() running at /usr/local/lib/python3.12/site-packages/starlette/middleware/base.py:151> cb=[TaskGroup._spawn.<locals>.task_done() at /usr/local/lib/python3.12/site-packages/anyio/_backends/_asyncio.py:794]> got Future <Future pending> attached to a different loop

It doesn't seem to make any difference if the fixtures are async or not.

Is there a good way of making this work? I can get by with a single client, of course, and manually specify the authorization header for every request. It'd be a lot more convenient if I didn't have to, though.