Peter writes that right now it's mostly centered around the input side of X.Org, the area where he works on. "Input testing is relatively simple with these tests since we can emulate virtually anything, but I'm not sure yet if such test cases can scale to output tests as well. Or even if there are tests that can be fully automatic without anyone staring at the screen. I know mesa already has such tests."
For those interested in this X.Org Server testing that will hopefully lead to fewer regressions in forthcoming releases, see Peter's blog post and mailing list post. Right now this X-specific testing code is being housed in the xorg-integration-tests Git repository.
Peter will be talking about this integration testing more next month from XDC2012.
Peter ends his mailing list post with, "also, to add a bit of trolling, I'm now tempted to merge the input drivers into the server repo..." This has been something that's been talked about in previous years but has yet to be acted upon. Interest in merging the graphics/output drivers has fizzled away but it looks like merging back the input drivers might happen.