assertThat(ArrayUtil.addAll((Object[]) null, (Object[]) null), is(nullValue()));
        assertThat(ArrayUtil.addAll(null, emptyArray).length, is(0));
        assertThat(ArrayUtil.addAll(emptyArray, null), is(sameInstance(emptyArray)));
        assertThat(ArrayUtil.addAll(emptyArray, null), is(sameInstance(emptyArray)));
        assertThat(ArrayUtil.addAll(emptyArray, emptyArray), is(sameInstance(emptyArray)));

      }
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterable<? extends E> elements) {
      checkNotNull(elements); // for GWT
      for (E element : elements) {
        add(checkNotNull(element));
      }
      return this;
    }

    @CanIgnoreReturnValue
    public Builder<E> addAll(Iterator<? extends E> elements) {
      checkNotNull(elements); // for GWT

        UnsupportedOperationException.class, () -> getList().addAll(0, MinimalCollection.of(e0())));
    expectUnchanged();
  }

  @ListFeature.Require(SUPPORTS_ADD_WITH_INDEX)
  @CollectionSize.Require(absent = ZERO)
  public void testAddAllAtIndex_supportedSomePresent() {
    assertTrue(
        "addAll(n, allPresent) should return true",
        getList().addAll(0, MinimalCollection.of(e0(), e3())));
    expectAdded(0, e0(), e3());

    assertEquals(HashMultiset.create(asList("a", "b", "b", "b", "c")), multiset);
  }

  public void testBuilderAddAllIterator() {
    Iterator<String> iterator = asList("a", "b", "a", "c").iterator();
    ImmutableMultiset<String> multiset =
        new ImmutableMultiset.Builder<String>().addAll(iterator).build();
    assertEquals(HashMultiset.create(asList("a", "b", "a", "c")), multiset);
  }

  }

  public void testBuilderAddAll_iterable() {
    List<String> a = asList("a", "b");
    List<String> b = asList("c", "d");
    ImmutableList<String> list = new ImmutableList.Builder<String>().addAll(a).addAll(b).build();
    assertEquals(asList("a", "b", "c", "d"), list);
    b.set(0, "f");
    assertEquals(asList("a", "b", "c", "d"), list);
  }

  public void testBuilderAddAll_iterator() {

    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());
    assertTrue("add(hasDuplicates) should return true", getSet().addAll(elementsToAdd));
    expectAdded(e3(), e4());
  }

    assertEquals(HashMultiset.create(asList("a", "b", "b", "b", "c")), multiset);
  }

  public void testBuilderAddAllIterator() {
    Iterator<String> iterator = asList("a", "b", "a", "c").iterator();
    ImmutableMultiset<String> multiset =
        new ImmutableMultiset.Builder<String>().addAll(iterator).build();
    assertEquals(HashMultiset.create(asList("a", "b", "a", "c")), multiset);
  }

  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testAddAll_emptySet() {
    assertFalse(getMultiset().addAll(Collections.<E>emptySet()));
    expectUnchanged();
  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testAddAll_emptyMultiset() {
    assertFalse(getMultiset().addAll(getSubjectGenerator().create()));
    expectUnchanged();
  }

  @CollectionFeature.Require(SUPPORTS_ADD)

    private final Adder adder;

    FailsToForwardReturnValue(Adder adder) {
      this.adder = adder;
    }

    @Override
    public int add(int a, int b) {
      return adder.add(a, b) + 1;
    }

    @Override
    public String toString() {
      return adder.toString();
    }
  }

  private static class FailsToPropagateException implements Adder {

    assertTrue(
        "addAll(allPresent) should return true", getList().addAll(MinimalCollection.of(e0())));
    expectAdded(e0());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAddAll_unsupportedAllPresent() {
    assertThrows(
        UnsupportedOperationException.class, () -> getList().addAll(MinimalCollection.of(e0())));
    expectUnchanged();