While reviewing bug 384339, Jeff wrote (iirc): { frankly, if I were to do it again I'd not have head/tail files; you get a setup function and a teardown function, and you put whatever you want in them (or not define them if not necessary) and you could load files if you wanted to keep common functionality separate make the dependencies explicit, not implicit by location that's long-term, not for now }

Bug 503613 has removed the tail file functionality, so updating title. I agree with comment 0 that it'd be good to make the dependencies explicit, this would be especially good for helping eslint to work better. For that, I think we really need bug 1308512 to give us a better module/file import system.