@Test
public void executeDiff() {

  Object object1 = new Object();
  Object object2 = new Object();
  Object object3 = new Object();
  List<Object> objectList1 = new ArrayList<Object>();
  List<Object> objectList2 = new ArrayList<Object>();
  objectList1.add(object1);
  objectList1.add(object2);
  objectList2.add(object2);
  objectList2.add(object3);
  doReturn(criteria).when(diffCriteria).getLeftCriteria();
  doReturn(criteria).when(diffCriteria).getRightCriteria();
  doReturn(objectList1).doReturn(objectList2).when(handler).execute(criteria);
  List<Object> actualObjects = handler.executeDiff(diffCriteria);
  assertEquals(object1, actualObjects.get(0));
}