JUnit Pioneer is an extension pack for JUnit 5 or, to be more precise, for the Jupiter engine. It is currently being set up, so this site as well as the repo is a little shy on content - we hope to fix that soon!
There are various ways to help us get there if you’re interested:
if you have an idea for an extension you could make good use of, open an issue
if you already wrote some code and would like to release it as part of JUnit Pioneer, which is an awesome idea, please also open an issue (rather than a pull request)