>> This doesn’t seem to exist in this case, which may simply be the deal breaker.

Perhaps, but perhaps not. The reason tests are valuable in these scenarios is they are actually a kind of system spec. LLMs can look at them to figure out how a system should (and should not) behave, and use that to guide the implementation.

I don’t see why regular specs (e.g. markdown files) could not serve the same purpose. Of course, most GitHub projects don’t include such files, but maybe that will change as time goes on.