@Test
public void testOccurrenceItemIds() throws MalformedURLException {

  TopicIF type = builder.makeTopic();
  TopicIF topic = builder.makeTopic();
  OccurrenceIF occ = builder.makeOccurrence(topic, type, "duplicate");
  occ.addItemIdentifier(new URILocator("http://psi.example.org"));
  occ = builder.makeOccurrence(topic, type, "duplicate");
  occ.addItemIdentifier(new URILocator("http://psi.example.com"));
  DuplicateSuppressionUtils.removeDuplicates(topic);
  Assert.assertTrue("duplicate occurrence were not removed",
         topic.getOccurrences().size() == 1);
  occ = (OccurrenceIF) topic.getOccurrences().iterator().next();
  Assert.assertTrue("item IDs were not merged",
             occ.getItemIdentifiers().size() == 2);
}