Fastapi Integration Test Pattern

When to Use

Use when creating new integration tests for FastAPI endpoints within the T1D Companion codebase to ensure consistency and proper setup of the authentication and service-coordinator stack.

Procedure

1. Mount Target Router: Ensure the target router is mounted on a fresh FastAPI() instance.
2. Dependency Overrides: Use app.dependency_overrides to inject patched versions of get_db, require_active_user, and get_current_user.
3. Mock Coordinator: Attach a mock coordinator instance to app.state.coordinator to bypass production service chains.
4. Test Client: Use Starlette.testclient.TestClient for synchronous HTTP calls.
5. Async/Sync Verification: Mark test functions with @pytest.mark.asyncio for any async database or service logic assertions.
6. Teardown: Always include a fixture or finalizer to clear app.dependency_overrides after each test to prevent state pollution.

Pitfalls

• Pollution: Not resetting app.dependency_overrides makes tests flaky and dependent on execution order.
• Initialization: Omitting the mock coordinator in app.state almost always causes runtime errors in the Service layer.

Verification

Refer to tests/test_chat_integration.py and tests/test_api_auth.py for canonical implementations.

Source: ruskibeats/t1d — distributed by TomeVault.