@Test public void testInvalidFormatCitizenId() {

    assertFalse("Not Only Digit citizen-id, must be invalid",
                CitizenId.isValid("1a3456789101b"));
    assertFalse("citizen-id length more than 13, must be invalid",
                CitizenId.isValid("12345678910124"));
    assertFalse("citizen-id length less than 13, must be invalid", CitizenId.isValid("00000"));
}