private Target partialOverlap;
  private Target containsDuplicates;
  private Target nullSingleton;

  @Override
  public void setUp() throws Exception {
    super.setUp();

    empty = new Target(emptyCollection(), "empty");
    /*
     * We test that nullSingleton.retainAll(disjointList) does NOT throw a
     * NullPointerException when disjointList does not, so we can't use