When writing Janet, i enjoy the judge[0] style of testing because it's so interactive. I added emacs helpers, one for running existing tests and one for updating the tests. It made for a nice repl-like experience, especially nice when writing grammars[1].

[0] https://github.com/ianthehenry/judge

[1] https://github.com/minikomi/advent-of-code/blob/d73e0b622b26...