collection.retainAll(MinimalCollection.of(createSamplesArray())));
    expectContents(array);
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(SEVERAL)
  public void testRetainAll_duplicatesRemoved() {
    E[] array = createSamplesArray();
    array[1] = e0();
    collection = getSubjectGenerator().create(array);
    assertTrue(
        "containsDuplicates.retainAll(subset) should return true",