Unit tests for a C99 compiler [on hold]

Given a C99 implementation, can I find unit tests to check that the front end (up to IC generator) works as the Standard requires ?

Can you point some locations where unit tests for different C99 implementations are found ?

EDIT:

I know there are tests in all compilers. I ask about a concrete way how to use them. Especially a way how to use the tests from the big compilers, like gcc; it would be useful to use them if I knew how.