? (ImmutableValueGraph<N, V>) graph
        : new ImmutableValueGraph<N, V>(graph);
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this
   */
  @Deprecated
  public static <N, V> ImmutableValueGraph<N, V> copyOf(ImmutableValueGraph<N, V> graph) {
    return checkNotNull(graph);
  }

  @Override
  public ElementOrder<N> incidentEdgeOrder() {
    return ElementOrder.stable();

/** Tests for {@link ImmutableValueGraph} . */
@RunWith(JUnit4.class)
public class ImmutableValueGraphTest {

  @Test
  public void immutableValueGraph() {
    MutableValueGraph<String, Integer> mutableValueGraph = ValueGraphBuilder.directed().build();
    mutableValueGraph.addNode("A");
    ImmutableValueGraph<String, Integer> immutableValueGraph =
        ImmutableValueGraph.copyOf(mutableValueGraph);

/** Tests for {@link ImmutableValueGraph} . */
@RunWith(JUnit4.class)
public class ImmutableValueGraphTest {

  @Test
  public void immutableValueGraph() {
    MutableValueGraph<String, Integer> mutableValueGraph = ValueGraphBuilder.directed().build();
    mutableValueGraph.addNode("A");
    ImmutableValueGraph<String, Integer> immutableValueGraph =
        ImmutableValueGraph.copyOf(mutableValueGraph);

        .nodeOrder(graph.nodeOrder())
        .incidentEdgeOrder(graph.incidentEdgeOrder());
  }

  /**
   * Returns an {@link ImmutableValueGraph.Builder} with the properties of this {@link
   * ValueGraphBuilder}.
   *
   * <p>The returned builder can be used for populating an {@link ImmutableValueGraph}.
   *
   * <p>Note that the returned builder will always have {@link #incidentEdgeOrder} set to {@link

 * ImmutableValueGraph}.
 *
 * <p>You can create an immutable copy of an existing {@code ValueGraph} using {@link
 * ImmutableValueGraph#copyOf(ValueGraph)}:
 *
 * <pre>{@code
 * ImmutableValueGraph<Integer, Double> immutableGraph = ImmutableValueGraph.copyOf(graph);
 * }</pre>
 *
 * <p>Instances of {@link ImmutableValueGraph} do not implement {@link MutableValueGraph}

  MutableValueGraph<Integer, String> graph;

  @After
  public void validateGraphState() {
    assertStronglyEquivalent(graph, Graphs.copyOf(graph));
    assertStronglyEquivalent(graph, ImmutableValueGraph.copyOf(graph));

    Graph<Integer> asGraph = graph.asGraph();
    AbstractGraphTest.validateGraph(asGraph);
    assertThat(graph.nodes()).isEqualTo(asGraph.nodes());

  MutableValueGraph<Integer, String> graph;

  @After
  public void validateGraphState() {
    assertStronglyEquivalent(graph, Graphs.copyOf(graph));
    assertStronglyEquivalent(graph, ImmutableValueGraph.copyOf(graph));

    Graph<Integer> asGraph = graph.asGraph();
    AbstractGraphTest.validateGraph(asGraph);
    assertThat(graph.nodes()).isEqualTo(asGraph.nodes());