RuntimeError: Task attached to a different loop

Root cause

Background dispatcher and asyncio.Queue were initialized during a session-scoped FastAPI app fixture before pytest-asyncio reset the running loop for the individual test, so the webhook handler awaited an object bound to the stale event loop.

Minimal fix

Make the FastAPI app/client async fixtures function-scoped, create the dispatcher inside the active test event loop, and explicitly await application startup before yielding the AsyncClient. Avoid constructing asyncio tasks or queues at import time or in session-scoped fixtures.