I have spent some time working on developing some unit tests for Gtk+ using Check. You can check them out here:
cvs -d :pserver:firstname.lastname@example.org:/var/publiccvs co gtk+
You need Check installed in your box in order to be able to run the tests or otherwise these will be disabled at configure time. You can get Check from here. You can also get it with apt in a Debian like system just typing apt-get install check.
Once you have downloaded, configured and built the repository, you can type make check in order to run all the tests in the Gtk+project. If you just want to run my unit tests you can just run make check from inside the ut/ subdir, where I have put all my tests. You should also be able to browse my tests on-line using Bonsai.
My folk Dape is also working for the build-brigade. He is working on the continuous integration tool (buildbot), improving it with nice features that will come in handy when setting up a nice Buildbot for the entire Gnome project. Meanwhile, I have to thank him for setting up a buildbot for my version of Gtk+ (the version where I added my unit tests) and its dependencies here. From that view you can check the builds, the tests logs and even some great code coverage statistics that are very useful to know which code is actually being tested/executed by the tests I have developed.
If you are interested in this topic and want to contact us you can join #build-brigade IRC channel at GimpNet or subscribe to the build-brigade mailing list.