I've been toying around with the NetBSD unit testing framework called "ATF". Unlike other well-known FOSS unit testing software, ATF seems to have relatively comprehensive support for writing unit tests in C - which is quite important for a piece of C software.
In fact, it seems quite a few popular bits of FOSS software handling unit tests, embedded/API documentation, etc all support C rather poorly. I wonder why.
I've not linked the ATF stubs into the main build tree just yet. The ATF code can be found in the source tree under /test-suite/atf/ . It works enough for me to use "make check" on my iBook (yes, that's a pre-intel, PPC G4 iBook) to check that the basic changes I'm making to the HTTP parser code don't introduce new bugs.
I would love some help writing more unit tests though!