@MapFeature.Require(SUPPORTS_PUT)
  public void testPutIfAbsent_supportedAbsent() {
    assertNull(
        "putIfAbsent(notPresent, value) should return null", getMap().putIfAbsent(k3(), v3()));
    expectAdded(e3());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testPutIfAbsent_supportedPresent() {
    assertEquals(

   * first specified. That is, if multiple elements are {@linkplain Object#equals equal}, all except
   * the first are ignored.
   */
  public static <E> ImmutableSet<E> of(E e1, E e2, E e3) {
    return new RegularSetBuilderImpl<E>(3).add(e1).add(e2).add(e3).review().build();
  }

  /**
   * Returns an immutable set containing the given elements, minus duplicates, in the order each was

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_absent() {
    int distinct = getMultiset().elementSet().size();
    assertEquals("multiset.remove(absent, 0) didn't return 0", 0, getMultiset().remove(e3(), 2));
    assertEquals(distinct, getMultiset().elementSet().size());
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testRemove_occurrences_unsupported_absent() {

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_absent() {
    int distinct = getMultiset().elementSet().size();
    assertEquals("multiset.remove(absent, 0) didn't return 0", 0, getMultiset().remove(e3(), 2));
    assertEquals(distinct, getMultiset().elementSet().size());
  }

  @CollectionFeature.Require(absent = SUPPORTS_REMOVE)
  public void testRemove_occurrences_unsupported_absent() {

    assertFalse(
        "containsAll(partialOverlap) should return false",
        collection.containsAll(MinimalCollection.of(e0(), e3())));
  }

  public void testContainsAll_disjoint() {
    assertFalse(
        "containsAll(disjoint) should return false",
        collection.containsAll(MinimalCollection.of(e3())));
  }

  @CollectionFeature.Require(absent = ALLOWS_NULL_QUERIES)
  public void testContainsAll_nullNotAllowed() {

  protected final K k2() {
    return e2().getKey();
  }

  protected final V v2() {
    return e2().getValue();
  }

  protected final K k3() {
    return e3().getKey();
  }

  protected final V v3() {
    return e3().getValue();
  }

  protected final K k4() {
    return e4().getKey();
  }

  protected final V v4() {
    return e4().getValue();
  }

  }

  @Override
  protected Integer getKeyNotInPopulatedMap() {
    return 3;
  }

  @Override
  protected UnhashableObject getValueNotInPopulatedMap() {
    return new Unhashables().e3();
  }

  protected final K k2() {
    return e2().getKey();
  }

  protected final V v2() {
    return e2().getValue();
  }

  protected final K k3() {
    return e3().getKey();
  }

  protected final V v3() {
    return e3().getValue();
  }

  protected final K k4() {
    return e4().getKey();
  }

  protected final V v4() {
    return e4().getValue();
  }

    return MinimalCollection.of(e3(), e4());
  }

  protected MinimalCollection<E> emptyCollection() {
    return MinimalCollection.of();
  }

  protected final E e0() {
    return samples.e0();
  }

  protected final E e1() {
    return samples.e1();
  }

  protected final E e2() {
    return samples.e2();
  }

  protected final E e3() {
    return samples.e3();
  }

  protected Map<Object, Integer> makePopulatedMap() {
    Colliders colliders = new Colliders();
    return ImmutableMap.of(
        colliders.e0(), 0,
        colliders.e1(), 1,
        colliders.e2(), 2,
        colliders.e3(), 3);
  }

  @Override
  protected Object getKeyNotInPopulatedMap() {
    return new Colliders().e4();
  }

  @Override
  protected Integer getValueNotInPopulatedMap() {
    return 4;
  }