After my non-existant 0.3.0-devel release, I am now writing .phpt tests for Cerebral Cortex. So far (10 or so tests) they have managed to highlight one bug (in Crtx_Config)
I must say that using the new pear run-tests command created by Greg Beaver (based upon PHPs make test) has been a pleasure, though I had to fix one bug myself (It would run the same tests twice, I believe it is fixed in CVS HEAD)</p>
.phpt files are remarkably simple in their implementation and are a pleasure to write (mostly!).
If you are not familiar with .phpt files, check out this awesome introduction written by the PHP QA team.