@Test
  public void edgeOrder_none() {
    MutableNetwork<Integer, String> network =
        NetworkBuilder.directed().edgeOrder(unordered()).build();

    assertThat(network.edgeOrder()).isEqualTo(unordered());
    assertThat(network.nodeOrder()).isEqualTo(insertion()); // default
  }

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

      NetworkBuilder.directed().<String, String>immutable().addNode("B").build();

  public PackageSanityTests() {
    MutableNetwork<String, String> mutableNetworkA = NetworkBuilder.directed().build();
    mutableNetworkA.addNode("a");
    MutableNetwork<String, String> mutableNetworkB = NetworkBuilder.directed().build();
    mutableNetworkB.addNode("b");

    network.addNode(N1);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addNode(N2);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    network.addNode(N1);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addNode(N2);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

  }

  @Test
  public void transpose_undirectedNetwork() {
    MutableNetwork<Integer, String> undirectedGraph = NetworkBuilder.undirected().build();
    undirectedGraph.addEdge(N1, N2, E12);

    assertThat(transpose(undirectedGraph)).isSameInstanceAs(undirectedGraph);
  }

  @Test
  public void transpose_directedNetwork() {
    MutableNetwork<Integer, String> directedGraph =

    directedGraph = mutableDirectedGraph;
    undirectedGraph = mutableUndirectedGraph;

    MutableNetwork<Integer, String> mutableDirectedNetwork =
        NetworkBuilder.directed().allowsParallelEdges(true).allowsSelfLoops(true).build();
    MutableNetwork<Integer, String> mutableUndirectedNetwork =
        NetworkBuilder.undirected().allowsParallelEdges(true).allowsSelfLoops(true).build();

      NetworkBuilder.directed().<String, String>immutable().addNode("B").build();

  public PackageSanityTests() {
    MutableNetwork<String, String> mutableNetworkA = NetworkBuilder.directed().build();
    mutableNetworkA.addNode("a");
    MutableNetwork<String, String> mutableNetworkB = NetworkBuilder.directed().build();
    mutableNetworkB.addNode("b");

    NetworkBuilder<N, E1> newBuilder = cast();
    newBuilder.edgeOrder = checkNotNull(edgeOrder);
    return newBuilder;
  }

  /** Returns an empty {@link MutableNetwork} with the properties of this {@link NetworkBuilder}. */
  public <N1 extends N, E1 extends E> MutableNetwork<N1, E1> build() {
    return new StandardMutableNetwork<>(this);
  }

  @SuppressWarnings("unchecked")

    Random gen = new Random(42); // Fixed seed so test results are deterministic.

    for (int trial = 0; trial < NUM_TRIALS; ++trial) {
      MutableNetwork<Integer, Object> network =
          networkBuilder.allowsParallelEdges(true).allowsSelfLoops(true).build();

      assertThat(network.nodes()).isEmpty();
      assertThat(network.edges()).isEmpty();

  final boolean graphIsMutable() {
    return networkAsMutableNetwork != null;
  }

  @Before
  public void init() {
    network = createGraph();
    if (network instanceof MutableNetwork) {
      networkAsMutableNetwork = (MutableNetwork<Integer, String>) network;
    }
  }

  @After
  public void validateNetworkState() {
    validateNetwork(network);
  }