@Test
    public void test_isValid_emptyValue() {
        final ConstraintValidatorContext context = null;
        assertTrue(validator.isValid("", context));
    }

    @Test
    public void test_determineValid_nullAndBlank() {
        assertTrue(validator.determineValid(null));
        assertTrue(validator.determineValid(""));
        assertTrue(validator.determineValid(" "));
        assertTrue(validator.determineValid("   "));