*
   * @throws IllegalArgumentException if {@code incidentEdgeOrder} is not either {@code
   *     ElementOrder.unordered()} or {@code ElementOrder.stable()}.
   * @since 29.0
   */
  public <N1 extends N> GraphBuilder<N1> incidentEdgeOrder(ElementOrder<N1> incidentEdgeOrder) {
    checkArgument(
        incidentEdgeOrder.type() == ElementOrder.Type.UNORDERED
            || incidentEdgeOrder.type() == ElementOrder.Type.STABLE,

  private final ElementOrder<N> incidentEdgeOrder;

  /** Constructs a mutable graph with the properties specified in {@code builder}. */
  StandardMutableValueGraph(AbstractGraphBuilder<? super N> builder) {
    super(builder);
    incidentEdgeOrder = builder.incidentEdgeOrder.cast();
  }

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

  @Override

    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateTShapedGraph();

    assertThat(graph.adjacentNodes(1)).containsExactly(2, 4, 3).inOrder();
  }

  @Test
  public void stableIncidentEdgeOrder_predecessors_returnsInConnectingEdgeInsertionOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateStarShapedGraph();

    assertThat(graph.adjacentNodes(1)).containsExactly(2, 4, 3, 5).inOrder();
  }

  @Test
  public void stableIncidentEdgeOrder_predecessors_returnsInConnectingEdgeInsertionOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

  }

  @Test
  public void incidentEdgeOrder_unordered() {
    graph = ValueGraphBuilder.directed().incidentEdgeOrder(ElementOrder.unordered()).build();
    assertThat(graph.incidentEdgeOrder()).isEqualTo(ElementOrder.unordered());
  }

  @Test
  public void incidentEdgeOrder_stable() {
    graph = ValueGraphBuilder.directed().incidentEdgeOrder(ElementOrder.stable()).build();

  }

  @Test
  public void incidentEdgeOrder_unordered() {
    graph = ValueGraphBuilder.directed().incidentEdgeOrder(ElementOrder.unordered()).build();
    assertThat(graph.incidentEdgeOrder()).isEqualTo(ElementOrder.unordered());
  }

  @Test
  public void incidentEdgeOrder_stable() {
    graph = ValueGraphBuilder.directed().incidentEdgeOrder(ElementOrder.stable()).build();

   * @throws IllegalArgumentException if {@code incidentEdgeOrder} is not either {@code
   *     ElementOrder.unordered()} or {@code ElementOrder.stable()}.
   * @since 29.0
   */
  public <N1 extends N> ValueGraphBuilder<N1, V> incidentEdgeOrder(
      ElementOrder<N1> incidentEdgeOrder) {
    checkArgument(
        incidentEdgeOrder.type() == ElementOrder.Type.UNORDERED
            || incidentEdgeOrder.type() == ElementOrder.Type.STABLE,

  private UndirectedGraphConnections(Map<N, V> adjacentNodeValues) {
    this.adjacentNodeValues = checkNotNull(adjacentNodeValues);
  }

  static <N, V> UndirectedGraphConnections<N, V> of(ElementOrder<N> incidentEdgeOrder) {
    switch (incidentEdgeOrder.type()) {
      case UNORDERED:
        return new UndirectedGraphConnections<>(
            new HashMap<N, V>(INNER_CAPACITY, INNER_LOAD_FACTOR));
      case STABLE:

    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateTShapedGraph();

    assertThat(graph.adjacentNodes(1)).containsExactly(2, 4, 3).inOrder();
  }

  @Test
  public void stableIncidentEdgeOrder_predecessors_returnsInConnectingEdgeInsertionOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateStarShapedGraph();

    assertThat(graph.adjacentNodes(1)).containsExactly(2, 4, 3, 5).inOrder();
  }

  @Test
  public void stableIncidentEdgeOrder_predecessors_returnsInConnectingEdgeInsertionOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);