I was working on this in branches/phpunit-restructure
I've merged it into head as of http://www.mediawiki.org/wiki/Special:Code/MediaWiki/72566
Essentially, it's just organizing our PHPUnit tests the way the rest of the world does, as a mirrored directory structure to the units under test. Also, we need to avoid like the plaugue making too much crazy custom phpunit invokation scripts, as was done previously, because it locks our tests down to a really specific version of phpunit, which is thankfully under constant development.
In short, use things as they are meant to be used... We probably reinvent too many wheels around here.
- Trevor