Add comprehensive tests for playlist service and refactor socket service tests

- Introduced a new test suite for the PlaylistService covering various functionalities including creation, retrieval, updating, and deletion of playlists.
- Added tests for handling sounds within playlists, ensuring correct behavior when adding/removing sounds and managing current playlists.
- Refactored socket service tests for improved readability by adjusting function signatures.
- Cleaned up unnecessary whitespace in sound normalizer and sound scanner tests for consistency.
- Enhanced audio utility tests to ensure accurate hash and size calculations, including edge cases for nonexistent files.
- Removed redundant blank lines in cookie utility tests for cleaner code.

tests/services/test_socket_service.py

@@ -97,7 +97,9 @@ class TestSocketManager:
     @pytest.mark.asyncio
     @patch("app.services.socket.extract_access_token_from_cookies")
     @patch("app.services.socket.JWTUtils.decode_access_token")
-    async def test_connect_handler_success(self, mock_decode, mock_extract_token, socket_manager, mock_sio):
+    async def test_connect_handler_success(
+        self, mock_decode, mock_extract_token, socket_manager, mock_sio
+    ):
         """Test successful connection with valid token."""
         # Setup mocks
         mock_extract_token.return_value = "valid_token"
@@ -130,7 +132,9 @@ class TestSocketManager:
 
     @pytest.mark.asyncio
     @patch("app.services.socket.extract_access_token_from_cookies")
-    async def test_connect_handler_no_token(self, mock_extract_token, socket_manager, mock_sio):
+    async def test_connect_handler_no_token(
+        self, mock_extract_token, socket_manager, mock_sio
+    ):
         """Test connection with no access token."""
         # Setup mocks
         mock_extract_token.return_value = None
@@ -162,7 +166,9 @@ class TestSocketManager:
     @pytest.mark.asyncio
     @patch("app.services.socket.extract_access_token_from_cookies")
     @patch("app.services.socket.JWTUtils.decode_access_token")
-    async def test_connect_handler_invalid_token(self, mock_decode, mock_extract_token, socket_manager, mock_sio):
+    async def test_connect_handler_invalid_token(
+        self, mock_decode, mock_extract_token, socket_manager, mock_sio
+    ):
         """Test connection with invalid token."""
         # Setup mocks
         mock_extract_token.return_value = "invalid_token"
@@ -195,7 +201,9 @@ class TestSocketManager:
     @pytest.mark.asyncio
     @patch("app.services.socket.extract_access_token_from_cookies")
     @patch("app.services.socket.JWTUtils.decode_access_token")
-    async def test_connect_handler_missing_user_id(self, mock_decode, mock_extract_token, socket_manager, mock_sio):
+    async def test_connect_handler_missing_user_id(
+        self, mock_decode, mock_extract_token, socket_manager, mock_sio
+    ):
         """Test connection with token missing user ID."""
         # Setup mocks
         mock_extract_token.return_value = "token_without_user_id"