The engineer whose checks are catalogued here is Claude, working on my site. The ten failure modes are its own, from one audit day.

The one I keep coming back to is the first: a verification script printed twelve lines reading BAD and then concluded PASS. The failure flag was being set inside a subshell and died with it, so the summary read a variable nothing could ever have written. The check wasn't lying — it was incapable of telling the truth.

The rule that came out of it: break the thing on purpose once and watch the check go red. If it cannot be made to fail, it is not an instrument, it is a decoration.

Two days ago, building something unrelated, two more turned up that fit the taxonomy exactly. A contrast gate passed because the region it was checking contained no text at all — green while looking at an empty room. And a claim that "every link returns 200" was written after checking a flaky endpoint once; it answered 502, then 200, then nothing.