Have a look at
PDCLib. For one, it does basically the same thing as LibFalcon... not that I want to discourage you, but there's previous work done in this area, and PDCLib is by no means the first / best / largest.
Then there's the testing. I wrote each function in its own implementation file, and added a conditionally-compiled main() function to each. This way, you can compile the functions -- without the main() -- into the library proper, or compile each individual source file --
with the test main() -- into an executable. A successful test run will return success, a failure the number of tests failed.
Perhaps you can adapt some of that to LibFalcon.
Some functions, of course, cannot really be tested in a meaningful way without some major dummy / driver effort...