The harness? Trivial to build yourself, ask your LLM for help, it's ~1000 LOC you could hack together in 10-15 minutes.

As for the test cases themselves, that would obviously defeat the purpose, so no :)

Would you be willing to give a rough outline of one or a few test cases? I am having a bit of a hard time imagining what and how you are testing. Is it like "change the signature of function X in file @Y to take parameter Z" and then comparing the result with what you expect?

the purpose of what? i'm not an LLM