@Test
public void testObserver() {
Subject subjectToChange = new Subject();
Observer textObserver = new TextObserver(subjectToChange);
Observer numObserver = new NumObserver(subjectToChange);
subjectToChange.setState("thisIsText");
assertTrue("thisIsText".equals(textObserver.getLastState()));
assertNull(numObserver.getLastState());
subjectToChange.setState("123456");
assertTrue("123456".equals(numObserver.getLastState()));
assertTrue("thisIsText".equals(textObserver.getLastState()));
subjectToChange.detach(textObserver);
subjectToChange.setState("thisIsTextAgain");
assertTrue("thisIsText".equals(textObserver.getLastState()));
assertTrue("123456".equals(numObserver.getLastState()));
}
