BeforeAndAfter { public Set<T> getAddedItems() { final HashSet<T> added = new HashSet<>(after); added.removeAll(before); return added; }  Set<T> getAddedItems(); Set<T> getRemovedItems(); Set<T> getIntersectedItems(); Set<T> getUnionedItems();  }
@Test public void testGetAddedItems() { assertEquals(new HashSet<>(asList(item4)), beforeAndAfter.getAddedItems()); }