[jeroenhd]

I can't think of any project I've worked on where external test suites even make sense. I suppose it would work when you have a very clear spec or compliance document you could write independent tests, or if you're rewriting a system and need the public API to be bug-for-bug compatible with the old one, but other than those niche use cases I wouldn't want to keep those tests external at all.

Even if you do have external tests, you still need internal ones for the surface area your external tests don't check for. Unit tests and such don't make sense at all combined with a separate test repo.