.withFeatures(CollectionSize.SEVERAL, CollectionFeature.ALLOWS_NULL_VALUES)
            .createTestSuite());

    suite.addTestSuite(SetViewTest.class);
    return suite;
  }

  public void testUnion_isView() {
    Set<Integer> set1 = newHashSet(1, 2);
    Set<Integer> set2 = newHashSet(2, 3);
    Set<Integer> union = union(set1, set2);
    assertThat(union).containsExactly(1, 2, 3);
    set1.add(0);