test: update conftest to use db_conn override on fastapi app

src/backend/tests/conftest.py

@@ -38,6 +38,7 @@
 from app.central import central_crud, central_schemas
 from app.central.central_schemas import ODKCentralDecrypted, ODKCentralIn
 from app.config import encrypt_value, settings
+from app.db.database import db_conn
 from app.db.enums import TaskStatus, UserRole, get_action_for_status_change
 from app.db.models import DbProject, DbTask, DbTaskHistory
 from app.main import get_application
@@ -329,6 +330,10 @@ async def project_data():
 @pytest_asyncio.fixture(scope="function")
 async def client(app: FastAPI, db: AsyncConnection):
     """The FastAPI test server."""
+    # Override server db connection to use same as in conftest
+    # NOTE this is marginally slower, but required else tests fail
+    app.dependency_overrides[db_conn] = lambda: db
+
     async with LifespanManager(app) as manager:
         async with AsyncClient(
             transport=ASGITransport(app=manager.app),