Reproduce

Follow the testing part of the documentation:
https://pgjones.gitlab.io/quart/how_to_guides/startup_shutdown.html#testing

AttributeError: 'async_generator' object has no attribute 'test_client'

The app fixture is not created as an async fixture which results in breaking the second part of the documentation where we attempt to access the test_client() it gives an async_generator.

Expected

The tests work successfully and I don't receive an async generator error
Environment:

• Python version:3.12.2
• Quart version:0.19.5