// Ideally, the ordering in test should never be updated.
  @Test
  public void stableIncidentEdgeOrder_edges_returnsInStableOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateStarShapedGraph();

    assertThat(graph.edges())
        .containsExactly(
            EndpointPair.ordered(2, 1),
            EndpointPair.ordered(1, 4),

    assertThat(network.edgeOrder())
        .isEqualTo(ElementOrder.sorted(Ordering.<String>natural().reverse()));
    assertThat(network.edges()).containsExactly("p", "i", "e").inOrder();
    assertThat(network.nodeOrder()).isEqualTo(ElementOrder.insertion()); // default
  }

  // Combined node and edge order tests

  @Test
  public void nodeOrderUnorderedAndEdgesSorted() {
    MutableNetwork<Integer, String> network =

      return network.outEdges(node);
    }

    @Override
    public EndpointPair<N> incidentNodes(E edge) {
      return network.incidentNodes(edge);
    }

    @Override
    public Set<E> adjacentEdges(E edge) {
      return network.adjacentEdges(edge);
    }

    // _don't_ override edge*Connecting*; we want the behavior from AbstractNetwork
  }

  // Ideally, the ordering in test should never be updated.
  @Test
  public void stableIncidentEdgeOrder_edges_returnsInStableOrder() {
    assume().that(graph.incidentEdgeOrder().type()).isEqualTo(ElementOrder.Type.STABLE);

    populateTShapedGraph();

    assertThat(graph.edges())
        .containsExactly(
            EndpointPair.unordered(1, 2),
            EndpointPair.unordered(1, 4),

          } catch (CancellationException e) {
            assertTrue(merger == Merger.allMerger);
            inputs.assertHasImmediateCancel(iFuture, jFuture, e);
          } catch (ExecutionException e) {
            assertTrue(merger == Merger.allMerger);
            inputs.assertHasImmediateFailure(iFuture, jFuture, e);
          } catch (TimeoutException e) {

  }

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

    Set<String> edges = network.edges();
    UnsupportedOperationException e =
        assertThrows(UnsupportedOperationException.class, () -> edges.add(E12));
    addEdge(N1, N2, E12);
    assertThat(network.edges()).containsExactlyElementsIn(edges);
  }

  @Override
  @Test

    // TODO(dbeaumont): Switch to static factory methods for creation now that class is final.
    // TODO(dbeaumont): Support escapers where alphanumeric chars are not safe.
    checkNotNull(safeChars); // eager for GWT.
    // Avoid any misunderstandings about the behavior of this escaper
    if (safeChars.matches(".*[0-9A-Za-z].*")) {
      throw new IllegalArgumentException(

      ArrayList<Object> edgeList = new ArrayList<>(network.edges());

      assertThat(network.nodes()).hasSize(NUM_NODES);
      assertThat(network.edges()).hasSize(NUM_EDGES);
      AbstractNetworkTest.validateNetwork(network);

      Collections.shuffle(edgeList, gen);
      int numEdgesToRemove = gen.nextInt(NUM_EDGES);
      for (int i = 0; i < numEdgesToRemove; ++i) {
        Object edge = edgeList.get(i);

 *   <li>graphs whose nodes/edges are insertion-ordered, sorted, or unordered
 *   <li>graphs whose edges have associated values
 * </ul>
 *
 * <p>{@code ValueGraph}, as a subtype of {@code Graph}, explicitly does not support parallel edges,
 * and forbids implementations or extensions with parallel edges. If you need parallel edges, use
 * {@link Network}. (You can use a positive {@code Integer} edge value as a loose representation of

    assertThat(edges).hasSize(2);
    assertThat(edges).contains(EndpointPair.unordered(N1, N1));
    assertThat(edges).contains(EndpointPair.unordered(N1, N2));
    assertThat(edges).contains(EndpointPair.unordered(N2, N1)); // equal to unordered(N1, N2)

    // ordered endpoints not compatible with undirected graph
    assertThat(edges).doesNotContain(EndpointPair.ordered(N1, N2));