feat: enhance test data cleanup by dropping MongoDB test database if applicable

backend/db/db.py

@@ -579,8 +579,14 @@ def ensure_mongodb_indexes(client=None, db_name=None):
             coll.create_index(keys, **kwargs)
 
 
-# Clear test collections at import time so tests start with a clean slate.
+# Clear test data at import time so tests start with a clean slate.
 if os.environ.get('DB_ENV', 'prod') == 'test':
+    if USE_MONGODB:
+        # Drop the entire MongoDB test database for a fresh start. Only do this
+        # for clearly test/e2e database names as a safety guard.
+        if _mongo_db_name and _mongo_db_name.endswith(('_test', '_e2e')):
+            get_mongo_client().drop_database(_mongo_db_name)
+    else:
         child_db.truncate()
         task_db.truncate()
         routine_db.truncate()