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/credit.py

@@ -30,7 +30,7 @@ class InsufficientCreditsError(Exception):
         self.required = required
         self.available = available
         super().__init__(
-            f"Insufficient credits: {required} required, {available} available"
+            f"Insufficient credits: {required} required, {available} available",
         )
 
 
@@ -138,10 +138,10 @@ class CreditService:
 
         """
         action = get_credit_action(action_type)
-        
+
         # Only deduct if action requires success and was successful, or doesn't require success
         should_deduct = (action.requires_success and success) or not action.requires_success
-        
+
         if not should_deduct:
             logger.info(
                 "Skipping credit deduction for user %s: action %s failed and requires success",
@@ -150,7 +150,7 @@ class CreditService:
             )
             # Still create a transaction record for auditing
             return await self._create_transaction_record(
-                user_id, action, 0, success, metadata
+                user_id, action, 0, success, metadata,
             )
 
         session = self.db_session_factory()
@@ -380,4 +380,4 @@ class CreditService:
                 raise ValueError(msg)
             return user.credits
         finally:
-            await session.close()
+            await session.close()