Add tests for gcm via cipher
diff --git a/tests/suites/test_suite_gcm.function b/tests/suites/test_suite_gcm.function
index c00ec0b..2b870d1 100644
--- a/tests/suites/test_suite_gcm.function
+++ b/tests/suites/test_suite_gcm.function
@@ -95,6 +95,7 @@
         }
         else
         {
+            TEST_ASSERT( ret == 0 );
             hexify( dst_str, output, pt_len );
 
             TEST_ASSERT( strcmp( (char *) dst_str, pt_result ) == 0 );