unit-tests: Make fixture functions optional

src/libstrongswan/tests/test_runner.c

@@ -186,14 +186,20 @@ static bool call_fixture(test_case_t *tcase, bool up)
 		if (test_restore_point())
 		{
 			if (up)
+			{
+				if (fixture->setup)
 				{
 					fixture->setup();
 				}
+			}
 			else
+			{
+				if (fixture->teardown)
 				{
 					fixture->teardown();
 				}
 			}
+		}
 		else
 		{
 			failure = TRUE;