I recently moved my project guardrails into a separate set of skills in a repo that I can bring into a new project fairly easily. It's focused (wrong word, it's seriously not focused) on implemented as many different levels of testing as I can think of. Right now it does this https://github.com/onion2k/guardrails/blob/main/GUARDRAILS.m....

The goal is to get to a point where I can say with a good level of confidence that a change didn't break anything. It might be the wrong change, and it might be crap code, but I can ship it without anything blowing up. I've been using it for a while across a few game projects and so far it's worked quite well.