testgdate: Exit with failure if there are not passed tests

tests/testgdate.c

@@ -8,6 +8,7 @@
 #include "glib.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <locale.h>
 #include <time.h>
@@ -506,7 +507,7 @@ g_print ("testing %d years\n", n_check_years);
   
   g_print("\n%u tests passed, %u failed\n",passed, notpassed);
 
-  return 0;
+  return (notpassed == 0) ? EXIT_SUCCESS : EXIT_FAILURE;
 }