### Question:
CheckQueryDetailsNullValidator implements ConstraintValidator<CheckQueryDetailsNull,
        List<ClientQueryField>>, ValidationErrorDescriptorBuilder { @Override public boolean isValid(List<ClientQueryField> value, ConstraintValidatorContext context) { return value == null; }  @Override void initialize(CheckQueryDetailsNull constraintAnnotation); @Override boolean isValid(List<ClientQueryField> value, ConstraintValidatorContext context); @Override ErrorDescriptor build(ConstraintViolation violation);  }### Answer:
@Test public void isValid_ValueNull_returnTrue() { ConstraintValidatorContext validatorContext = mock(ConstraintValidatorContext.class); assertTrue(validator.isValid(null, validatorContext)); }
@Test public void isValid_ValueNotNull_returnFalse() { ConstraintValidatorContext validatorContext = mock(ConstraintValidatorContext.class); assertFalse(validator.isValid(new ArrayList<ClientQueryField>(), validatorContext)); }