[development] Drupal Test Suites

I've been working on several Drupal projects for work and am thinking of getting an install of PHPUnderControl (http://www.phpundercontrol.org) and was wondering if there's any tests for Drupal core that are publicly available I'd be able to drop into the test suite. If not I think this would be something worth putting some time into, even as a regular project on the site. Since all the modules we write depend, in some way, on the core code, being able to include a generic core test suite in with our own would probably prove to be pretty useful. Especially for those of us that find ourselves needing to occasionally dig into core code now and then.