### Question:
FirstNameValidator implements PersonValidator { @Override public boolean validate(Person person) { return person.getFirstName() != null; }  @Override boolean validate(Person person);  }### Answer:
@Test public void fullNameValidator_returnsTrueWhenFirstNameIsSet(){ Person john = new Person("John", "Quincy", "Adams"); assertTrue(firstNameValidator.validate(john)); john = new Person("John", null, "Adams"); assertTrue(firstNameValidator.validate(john)); john = new Person("John", "Quincy", null); assertTrue(firstNameValidator.validate(john)); }
@Test public void fullNameValidator_returnsFalseWhenFirstNameNotSet(){ Person john = new Person(null, "Quincy", "Adams"); assertFalse(firstNameValidator.validate(john)); }