### Question:
NullValidator implements ConstraintValidator<Null, Object> { public boolean isValid(Object object, ConstraintValidatorContext constraintValidatorContext) { return object == null; }  void initialize(Null constraintAnnotation); boolean isValid(Object object, ConstraintValidatorContext constraintValidatorContext);  }### Answer:
@Test public void testIsValid() { assertTrue( constraint.isValid( null, null ) ); assertFalse( constraint.isValid( new Object(), null ) ); }