Refactor test files for improved readability and consistency

- Removed unnecessary blank lines and adjusted formatting in test files.
- Ensured consistent use of commas in function calls and assertions across various test cases.
- Updated import statements for better organization and clarity.
- Enhanced mock setups in tests for better isolation and reliability.
- Improved assertions to follow a consistent style for better readability.

app/services/playlist.py

@@ -49,7 +49,7 @@ class PlaylistService:
         if not main_playlist:
             raise HTTPException(
                 status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-                detail="Main playlist not found. Make sure to run database seeding."
+                detail="Main playlist not found. Make sure to run database seeding.",
             )
 
         return main_playlist
@@ -179,7 +179,7 @@ class PlaylistService:
         return await self.playlist_repo.get_playlist_sounds(playlist_id)
 
     async def add_sound_to_playlist(
-        self, playlist_id: int, sound_id: int, user_id: int, position: int | None = None
+        self, playlist_id: int, sound_id: int, user_id: int, position: int | None = None,
     ) -> None:
         """Add a sound to a playlist."""
         # Verify playlist exists
@@ -202,11 +202,11 @@ class PlaylistService:
 
         await self.playlist_repo.add_sound_to_playlist(playlist_id, sound_id, position)
         logger.info(
-            "Added sound %s to playlist %s for user %s", sound_id, playlist_id, user_id
+            "Added sound %s to playlist %s for user %s", sound_id, playlist_id, user_id,
         )
 
     async def remove_sound_from_playlist(
-        self, playlist_id: int, sound_id: int, user_id: int
+        self, playlist_id: int, sound_id: int, user_id: int,
     ) -> None:
         """Remove a sound from a playlist."""
         # Verify playlist exists
@@ -228,7 +228,7 @@ class PlaylistService:
         )
 
     async def reorder_playlist_sounds(
-        self, playlist_id: int, user_id: int, sound_positions: list[tuple[int, int]]
+        self, playlist_id: int, user_id: int, sound_positions: list[tuple[int, int]],
     ) -> None:
         """Reorder sounds in a playlist."""
         # Verify playlist exists
@@ -262,7 +262,7 @@ class PlaylistService:
         await self._unset_current_playlist(user_id)
         await self._set_main_as_current(user_id)
         logger.info(
-            "Unset current playlist and set main as current for user %s", user_id
+            "Unset current playlist and set main as current for user %s", user_id,
         )
 
     async def get_playlist_stats(self, playlist_id: int) -> dict[str, Any]:
@@ -290,7 +290,7 @@ class PlaylistService:
 
         # Check if sound is already in main playlist
         if not await self.playlist_repo.is_sound_in_playlist(
-            main_playlist.id, sound_id
+            main_playlist.id, sound_id,
         ):
             await self.playlist_repo.add_sound_to_playlist(main_playlist.id, sound_id)
             logger.info(