expectReturnsFalse(containsDuplicates);
    expectContents(e0());
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testRetainAll_containsDuplicatesSizeSeveral() {
    expectReturnsTrue(containsDuplicates);
    expectContents(e0());
  }

  // retainAll(nullSingleton)

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)