mutation-testing

A green suite proves nothing if a fake can pass it. I fed three fake implementations into my 32-test selftest to prove the grader works.

TL;DR: After my 32-test suite went green, I worried it might be vacuous, so I built three fake validators (always pass, always fail, always emit every error code) that must each score zero passes. This is manual mutation testing, a known technique. I also pinned the selftest's sha256 so silent grader edits get caught.