filtered2.clear();
        assertThat(unfiltered).containsExactlyElementsIn(inverseFiltered);
      }
    }
  }

  public abstract static class AbstractFilteredSetTest<C extends Set<Integer>>
      extends AbstractFilteredCollectionTest<C> {
    public void testEqualsAndHashCode() {
      for (List<Integer> contents : SAMPLE_INPUTS) {
        Set<Integer> expected = new HashSet<>();