Is this suitable?

    def test_find(self):
        # to track that at least one call to find_library() found something
        found = false
        for name in ("c", "m"):
            lib = find_library(name)
            if lib:
                found = true
                cdll.LoadLibrary(lib)
                CDLL(lib)
        # test is FAILED if nothing was found
        self.assertTrue(found)