@Test
 public void testEmailValidatorWithOkEmail() {
   Assert.assertTrue(validator.isValid("*****@*****.**"));
 }
 @Test
 public void testEmailValidatorWithEmptyString() {
   Assert.assertTrue(validator.isValid(""));
 }
 @Test
 public void testEmailValidatorWithFaultyString() {
   Assert.assertFalse(validator.isValid("not.an.email"));
 }
 @Test
 public void testEmailValidatorWithNull() {
   Assert.assertTrue(validator.isValid(null));
 }