Unhandled promise rejection in tests

RANKED DIAGNOSIS

What usually causes it

1. 01

   A promise was started without awaiting it

   The rejection escapes after the test moves on.

   DIAGNOSE

   Trace every created promise in the failing path and find the missing await or return.

   FIX

   Await the operation and assert its success or rejection explicitly.

2. 02

   Cleanup rejects after teardown

   A closed page, socket, or server can cause late asynchronous failures.

   DIAGNOSE

   Inspect teardown ordering and open handles.

   FIX

   Stop producers before closing their dependencies and await cleanup.

3. 03

   An event handler throws asynchronously

   Framework callbacks can reject outside the test's main promise chain.

   DIAGNOSE

   Capture application errors and identify the originating event.

   FIX

   Handle the error in the application and expose an observable failure state.