@Test
    public void test_customMessage() {
        CustomMessageBean bean = new CustomMessageBean();
        bean.setCronWithCustomMessage("invalid");

        Set<ConstraintViolation<CustomMessageBean>> violations = validator.validate(bean);
        assertFalse(violations.isEmpty());
        assertEquals(1, violations.size());

        ConstraintViolation<CustomMessageBean> violation = violations.iterator().next();