OutlinePageDestinations { public Set<Integer> getPages() { return Collections.unmodifiableSet(destinations.keySet()); }  void addPage(Integer page, String title); Set<Integer> getPages(); String getTitle(Integer page);  }
@Test public void testGetPages() { OutlinePageDestinations victim = new OutlinePageDestinations(); victim.addPage(1, "Title1"); victim.addPage(2, "Title2"); assertEquals(2, victim.getPages().size()); }