MutableGraph<N> subgraph =
        (nodes instanceof Collection)
            ? GraphBuilder.from(graph).expectedNodeCount(((Collection) nodes).size()).build()
            : GraphBuilder.from(graph).build();
    for (N node : nodes) {
      subgraph.addNode(node);
    }
    for (N node : subgraph.nodes()) {
      for (N successorNode : graph.successors(node)) {

    for (Integer node : graph.nodes()) {
      new EqualsTester()
          .addEqualityGroup(
              graph.predecessors(node), graph.successors(node), graph.adjacentNodes(node))
          .testEquals();
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = graph.nodes();

    ComparableSubClass node8 = new ComparableSubClass(8);

    graph.addNode(node4);
    graph.addNode(node2);
    graph.addNode(node6);
    graph.addNode(node8);

    assertThat(graph.nodeOrder().comparator()).isEqualTo(Ordering.natural());
    assertThat(graph.nodes()).containsExactly(node2, node4, node6, node8).inOrder();
  }

  private static void addNodes(MutableGraph<Integer> graph) {

   * equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}, and to
   * {@code edgeConnectingOrNull(nodeU, nodeV) != null}.
   *
   * <p>In an undirected network, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}.
   *
   * @since 23.0
   */
  boolean hasEdgeConnecting(N nodeU, N nodeV);

  /**

        nodes.add(node);
    }

    /**
     * find a node by the GAV (metadata)
     *
     * @param md
     */
    public MetadataGraphNode findNode(MavenArtifactMetadata md) {
        for (MetadataGraphNode mgn : nodes) {
            if (mgn.metadata.equals(md)) {
                return mgn;
            }
        }

        MetadataGraphNode node = new MetadataGraphNode(md);
        addNode(node);

  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test
  public void edges_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = network.nodes();
    assertThrows(UnsupportedOperationException.class, () -> nodes.add(N2));
    addNode(N1);
    assertThat(network.nodes()).containsExactlyElementsIn(nodes);
  }

  @Override
  @Test
  public void edges_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    checkNotNull(nodeU);
    checkNotNull(nodeV);
    return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
  }

  @Override
  public boolean hasEdgeConnecting(EndpointPair<N> endpoints) {
    checkNotNull(endpoints);
    if (!isOrderingCompatible(endpoints)) {
      return false;
    }
    N nodeU = endpoints.nodeU();
    N nodeV = endpoints.nodeV();

    for (Integer node : graph.nodes()) {
      new EqualsTester()
          .addEqualityGroup(
              graph.predecessors(node), graph.successors(node), graph.adjacentNodes(node))
          .testEquals();
    }
  }

  @Override
  @Test
  public void nodes_checkReturnedSetMutability() {
    assume().that(graphIsMutable()).isTrue();

    Set<Integer> nodes = graph.nodes();

      @Override
      public Set<N> adjacentNodes(N node) {
        return AbstractValueGraph.this.adjacentNodes(node);
      }

      @Override
      public Set<N> predecessors(N node) {
        return AbstractValueGraph.this.predecessors(node);
      }

      @Override
      public Set<N> successors(N node) {
        return AbstractValueGraph.this.successors(node);
      }

      @Override