protected final Multiset<E> getMultiset() {
    return (Multiset<E>) collection;
  }

  protected void initThreeCopies() {
    collection = getSubjectGenerator().create(e0(), e0(), e0());
  }

  public void testPutWithSameValueFails() {
    getMap().put(k0(), v0());
    assertThrows(IllegalArgumentException.class, () -> getMap().put(k1(), v0()));
    // verify that the bimap is unchanged
    expectAdded(e0());
  }

  @MapFeature.Require(SUPPORTS_PUT)
  @CollectionSize.Require(ZERO)
  public void testPutPresentKeyDifferentValue() {
    getMap().put(k0(), v0());
    getMap().put(k0(), v1());

  public static ImmutableDoubleArray of(double e0) {
    return new ImmutableDoubleArray(new double[] {e0});
  }

  /** Returns an immutable array containing the given values, in order. */
  public static ImmutableDoubleArray of(double e0, double e1) {
    return new ImmutableDoubleArray(new double[] {e0, e1});
  }

  /** Returns an immutable array containing the given values, in order. */

    return new ImmutableIntArray(new int[] {e0, e1, e2});
  }

  /** Returns an immutable array containing the given values, in order. */
  public static ImmutableIntArray of(int e0, int e1, int e2, int e3) {
    return new ImmutableIntArray(new int[] {e0, e1, e2, e3});
  }

  /** Returns an immutable array containing the given values, in order. */

  public void testLastIndexOf_duplicate() {
    E[] array = createSamplesArray();
    array[getNumElements() / 2] = e0();
    collection = getSubjectGenerator().create(array);
    assertEquals(
        "lastIndexOf(duplicate) should return index of last occurrence",
        getNumElements() / 2,
        getList().lastIndexOf(e0()));
  }

  public void testElement_size1() {
    assertEquals("size1Queue.element() should return first element", e0(), getQueue().element());
    expectUnchanged();
  }

  @CollectionFeature.Require(KNOWN_ORDER)
  @CollectionSize.Require(SEVERAL)
  public void testElement_sizeMany() {
    assertEquals("sizeManyQueue.element() should return first element", e0(), getQueue().element());
    expectUnchanged();
  }

  @CollectionSize.Require(absent = ZERO)
  public void testAddAll_supportedSomePresent() {
    assertTrue(
        "add(somePresent) should return true", getSet().addAll(MinimalCollection.of(e3(), e0())));
    expectAdded(e3());
  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testAddAll_withDuplicates() {
    MinimalCollection<E> elementsToAdd = MinimalCollection.of(e3(), e4(), e3(), e4());

    assertContentsAnyOrder(multimap().removeAll(k0()), v0());
    expectMissing(e0());
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemoveAllPropagatesToGet() {
    Collection<V> getResult = multimap().get(k0());

    multimap().removeAll(k0());

    assertEmpty(getResult);
    expectMissing(e0());
  }

  @CollectionSize.Require(SEVERAL)

  }

  @CollectionSize.Require(absent = ZERO)
  public void testContainsAll_subset() {
    assertTrue(
        "containsAll(subset) should return true",
        collection.containsAll(MinimalCollection.of(e0())));
  }

  public void testContainsAll_sameElements() {
    assertTrue(
        "containsAll(sameElements) should return true",
        collection.containsAll(MinimalCollection.of(createSamplesArray())));
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = ZERO)
  public void testRemove_present() {
    getSet().remove(e0());
    assertFalse(
        "After remove(present) a set should not contain the removed element.",
        getSet().contains(e0()));
  }