public void onChangeLevel_updatesObserverWithNewMoodImage() throws Exception {
when(level.getNormalMood()).thenReturn(DEFAULT_MOOD);
tamagotchi.start();
Level newLevel = mock(Level.class);
when(newLevel.getNormalMood()).thenReturn(new Image[] { HAPPY1 });
tamagotchi.onImageSetCallback();
tamagotchi.setLevel(newLevel);
tamagotchi.onImageSetCallback();