enemies = Sets.newHashSet("Dick", "Harry", "Tom");
  }

  public void testUnion() {
    Set<String> all = Sets.union(friends, enemies);
    assertEquals(5, all.size());

    ImmutableSet<String> immut = Sets.union(friends, enemies).immutableCopy();
    HashSet<String> mut = Sets.union(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Buck");
    assertEquals(6, all.size());

    assertThat(Multisets.union(ms1, ms2)).containsExactly("a", "a", "b", "b", "c");
  }

  public void testUnionEqualMultisets() {
    Multiset<String> ms1 = HashMultiset.create(Arrays.asList("a", "b", "a"));
    Multiset<String> ms2 = HashMultiset.create(Arrays.asList("a", "b", "a"));
    assertEquals(ms1, Multisets.union(ms1, ms2));
  }

  public void testUnionEmptyNonempty() {

    this.selfLoopCount = checkNonNegative(selfLoopCount);
    checkState(selfLoopCount <= inEdgeMap.size() && selfLoopCount <= outEdgeMap.size());
  }

  @Override
  public Set<N> adjacentNodes() {
    return Sets.union(predecessors(), successors());
  }

  @Override
  public Set<E> incidentEdges() {
    return new AbstractSet<E>() {
      @Override
      public UnmodifiableIterator<E> iterator() {

            .createTestSuite());

    suite.addTest(
        MultisetTestSuiteBuilder.using(unionGenerator())
            .withFeatures(CollectionSize.ANY, CollectionFeature.ALLOWS_NULL_VALUES)
            .named("Multisets.union")
            .createTestSuite());

    suite.addTest(
        MultisetTestSuiteBuilder.using(intersectionGenerator())
            .withFeatures(
                CollectionSize.ANY,

            .createTestSuite());

    suite.addTest(
        MultisetTestSuiteBuilder.using(unionGenerator())
            .withFeatures(CollectionSize.ANY, CollectionFeature.ALLOWS_NULL_VALUES)
            .named("Multisets.union")
            .createTestSuite());

    suite.addTest(
        MultisetTestSuiteBuilder.using(intersectionGenerator())
            .withFeatures(
                CollectionSize.ANY,

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this network.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *
   * <p>If {@code node} is removed from the network after this method is called, the {@code Set}

    TreeRangeSet<C> result = create();
    result.addAll(rangeSet);
    return result;
  }

  /**
   * Returns a {@code TreeRangeSet} representing the union of the specified ranges.
   *
   * <p>This is the smallest {@code RangeSet} which encloses each of the specified ranges. An
   * element will be contained in this {@code RangeSet} if and only if it is contained in at least

  }

  @Override
  public Set<E> adjacentEdges(E edge) {
    EndpointPair<N> endpointPair = incidentNodes(edge); // Verifies that edge is in this network.
    Set<E> endpointPairIncidentEdges =
        Sets.union(incidentEdges(endpointPair.nodeU()), incidentEdges(endpointPair.nodeV()));
    return edgeInvalidatableSet(
        Sets.difference(endpointPairIncidentEdges, ImmutableSet.of(edge)), edge);
  }

  @Override