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/models/credit_action.py

@@ -118,4 +118,4 @@ def get_all_credit_actions() -> dict[CreditActionType, CreditAction]:
         Dictionary of all credit actions
 
     """
-    return CREDIT_ACTIONS.copy()
+    return CREDIT_ACTIONS.copy()