NullPointerException.class, () -> multimap().putAll(k3(), newArrayList(v3(), null)));

    Collection<V> values = multimap().get(k3());
    if (values.size() == 0) {
      expectUnchanged();
      // Be extra thorough in case internal state was corrupted by the expected null.
      assertEquals(new ArrayList<>(), new ArrayList<>(values));
      assertEquals(size, multimap().size());
    } else {

      Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

      Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

   * {@code multimap}.
   */
  public <K extends K0, V extends V0> Multimap<K, V> build(
      Multimap<? extends K, ? extends V> multimap) {
    Multimap<K, V> result = build();
    result.putAll(multimap);
    return result;
  }

  /**
   * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
   *
   * @since 16.0
   */
  public abstract static class ListMultimapBuilder<

   * {@code multimap}.
   */
  public <K extends K0, V extends V0> Multimap<K, V> build(
      Multimap<? extends K, ? extends V> multimap) {
    Multimap<K, V> result = build();
    result.putAll(multimap);
    return result;
  }

  /**
   * A specialization of {@link MultimapBuilder} that generates {@link ListMultimap} instances.
   *
   * @since 16.0
   */
  public abstract static class ListMultimapBuilder<

    TreeMultimap<String, Integer> multimap = TreeMultimap.create();
    multimap.put("google", 2);
    multimap.put("google", 6);
    multimap.put("foo", 3);
    multimap.put("foo", 1);
    multimap.put("foo", 7);
    multimap.put("tree", 4);
    multimap.put("tree", 0);
    return multimap;
  }

  public void testToString() {
    SetMultimap<String, Integer> multimap = create();

    } catch (UnsupportedOperationException expected) {
    }
    assertMultimapRemainsUnmodified(multimap, originalEntries);

    // Test #putAll(Multimap<K, V>)
    Multimap<K, V> multimap2 = ArrayListMultimap.create();
    multimap2.put(sampleKey, sampleValue);
    try {
      multimap.putAll(multimap2);
      fail("putAll(Multimap<K, V>) succeeded on unmodifiable multimap");

   *
   * @throws NullPointerException if any key or value in {@code multimap} is null
   */
  public static <K, V> ImmutableSetMultimap<K, V> copyOf(
      Multimap<? extends K, ? extends V> multimap) {
    return copyOf(multimap, null);
  }

  private static <K, V> ImmutableSetMultimap<K, V> copyOf(
      Multimap<? extends K, ? extends V> multimap,
      @Nullable Comparator<? super V> valueComparator) {

    if (multimap.isEmpty()) {
      return of();
    }

    // TODO(lowasser): copy ImmutableSetMultimap by using asList() on the sets
    if (multimap instanceof ImmutableListMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;

      @Override
      protected Iterator<String> newTargetIterator() {
        multimap = create();
        multimap.putAll("foo", asList(2, 3));
        multimap.putAll("bar", asList(4, 5));
        multimap.putAll("foo", asList(6));
        multimap.putAll("baz", asList(7, 8));
        multimap.putAll("dog", asList(9));
        multimap.putAll("bar", asList(10, 11));