static void test_fail_message_va(const char *prefix, const char *file,
                                 int line, const char *type,
                                 const char *left, const char *right,
                                 const char *op, const char *fmt, va_list ap)
{
    test_fail_message_prefix(prefix, file, line, type, left, right, op);
    if (fmt != NULL) {
        test_vprintf_stderr(fmt, ap);
        test_printf_stderr("\n");
    }
    test_flush_stderr();
}