Rack (non Rails) support
It looks like it wouldn't be too hard to support non-rails Rack apps. While not as bad as a Rails app, testing a Rack-only app still suffers from the pain of booting the JVM + JRuby.
Hm well it would probably be possible but at the moment I cannot look into that. I would review and accept any pull requests for this though. Also note that @headius (maintainer of JRuby) is also working on a JRuby preloader, perhaps his is more framework-agnostic.
https://github.com/headius/boing Although it seems he also did not have time recently to update it much.
Cool, I'm in the same boat on not enough time at the moment, but if I can I'll try to get a PR together.