Simplify error handling in BackupAgent when a backup is not found (#139754)

Simplify error handling in BackupAgent when backup is not found

tests/components/backup/common.py

@@ -67,15 +67,20 @@ async def aiter_from_iter(iterable: Iterable) -> AsyncIterator:
 def mock_backup_agent(name: str, backups: list[AgentBackup] | None = None) -> Mock:
     """Create a mock backup agent."""
 
+    async def delete_backup(backup_id: str, **kwargs: Any) -> None:
+        """Mock delete."""
+        get_backup(backup_id)
+
     async def download_backup(backup_id: str, **kwargs: Any) -> AsyncIterator[bytes]:
         """Mock download."""
-        if not await get_backup(backup_id):
-            raise BackupNotFound
         return aiter_from_iter((backups_data.get(backup_id, b"backup data"),))
 
-    async def get_backup(backup_id: str, **kwargs: Any) -> AgentBackup | None:
+    async def get_backup(backup_id: str, **kwargs: Any) -> AgentBackup:
         """Get a backup."""
-        return next((b for b in backups if b.backup_id == backup_id), None)
+        backup = next((b for b in backups if b.backup_id == backup_id), None)
+        if backup is None:
+            raise BackupNotFound
+        return backup
 
     async def upload_backup(
         *,
@@ -99,7 +104,7 @@ def mock_backup_agent(name: str, backups: list[AgentBackup] | None = None) -> Mo
     mock_agent.unique_id = name
     type(mock_agent).agent_id = BackupAgent.agent_id
     mock_agent.async_delete_backup = AsyncMock(
-        spec_set=[BackupAgent.async_delete_backup]
+        side_effect=delete_backup, spec_set=[BackupAgent.async_delete_backup]
     )
     mock_agent.async_download_backup = AsyncMock(
         side_effect=download_backup, spec_set=[BackupAgent.async_download_backup]