Thanks for the ideas — you're right that automating the UI-oriented testing is more difficult. We're already piloting some ideas in this area (e.g Build your own React) — but the current focus is on perfecting what we have.

Our testers are all OSS. Here's our git tester for example — https://github.com/codecrafters-io/git-tester.

Others can be found on our GitHub org. https://github.com/codecrafters-io

We need to do a better job of exposing links to testers in our in-app UI — good feedback!