I've never liked having to type my test twice, once for the actual test and once for the 'message'. So I do something more like this instead:

  #include <stdio.h>
  #define test(expr) do {                              \
          if (!(expr)) printf("FAILED: %s\n", #expr);  \
          else printf("    ok: %s\n", #expr);          \
      } while (0)
  
  int main(void) {
      int a = 1;
      test(a == 1);
      test(a == 0);
      return 0;
  }

http://en.wikipedia.org/wiki/Assert.h

For those of you working in embedded environments where even that is too heavy: cross-compile or write that stupid macro yourself (it's 3 lines for pity's sake!).

Neat hack, but I far more enjoy glib's g_test_*() infrastructure. It also integrates well with `make' and can print out reports or store them for future comparisons.

Um 3 lines? That's not 3 lines. Sure it FITS into 3 lines but every time you see a ";" you also see a new line. So

#define mu_run_test(test) do { char message = test(); tests_run++; if (message) return message; } while (0)

Isn't one line but

  #define mu_run_test(test) do { 
  char *message = test();
  tests_run++; 
  if (message) 
    return message; 
  } while (0