private LoginFormValidator(
     LoginFormValidatable expected, LoginFormValidatable actual, Validator parent) {
   super(description, expected, actual, parent);
   this.expected = expected;
   this.actual = actual;
   addChildValidator(
       UsernameInputValidator.getInstance(
           expected.inUsernameInput(), actual.inUsernameInput(), this));
   addChildValidator(
       PasswordInputValidator.getInstance(
           expected.inPasswordInput(), actual.inPasswordInput(), this));
 }
 @Override
 protected void executeVerifications() {
   verify("Error Message", expected.getErrorMessage(), actual.getErrorMessage());
   verify(
       "'Sign In' button label", expected.getSignInButtonLabel(), actual.getSignInButtonLabel());
 }