}
    }
  }

  public abstract static class AbstractFilteredCollectionTest<C extends Collection<Integer>>
      extends AbstractFilteredIterableTest<C> {

    public void testReadsThroughAdd() {
      for (List<Integer> contents : SAMPLE_INPUTS) {
        C unfiltered = createUnfiltered(contents);
        C filterThenAdd = filter(unfiltered, EVEN);
        unfiltered.add(4);