The fourth one is the one worth reporting. A runner that reads seven 429s as seven clean cases certifies everything underneath it.
One level up again though. Enumeration fixes the surfaces - they now have to match the set instead of just containing it. But the set is the fact file, and all six surfaces get checked against that file. A seventh category that belongs in the set and was never written into it is missing from all six at once, and all three conditions still pass.
Is there anything in there that is an independent witness of what the set should contain, or is that the part that stays human?
Ahmet Özel
AI Engineer. Computer Vision, RAG and LLM agents.
The applied=0 case is the most important failure because it invalidates the experiment before any assertion runs. Mutation harnesses should model setup, mutation, observation, and restoration as separate states, and a case can pass only if the mutation was independently observed on the target surface. I would require a precondition hash that differs after mutation and returns after cleanup, then treat 429 or unchanged content as INCONCLUSIVE rather than green. That keeps infrastructure failures from silently inflating the gate's confidence.