assertThat(networkForTest.edgesConnecting(N1, N1)).containsExactly(E11);
    network.addEdge(N1, N2, E12);
    assertThat(networkForTest.edgesConnecting(N1, N2)).containsExactly(E12);
    assertThat(networkForTest.edgesConnecting(N1, N1)).containsExactly(E11);
  }

  @Test
  public void edgesConnecting_parallelEdges() {
    network.addEdge(N1, N2, E12);
    network.addEdge(N1, N2, E12_A);
    network.addEdge(N2, N1, E21);

    addEdge(N1, N1, E11);
    addEdge(N1, N1, E11_A);
    addEdge(N1, N2, E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11_A));
    assertThat(network.edgesConnecting(N1, N1)).containsExactly(E11);
    assertThat(network.edgesConnecting(N1, N2)).containsExactly(E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11));
    assertThat(network.edgesConnecting(N1, N1)).isEmpty();

    addEdge(N1, N1, E11);
    addEdge(N1, N1, E11_A);
    addEdge(N1, N2, E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11_A));
    assertThat(network.edgesConnecting(N1, N1)).containsExactly(E11);
    assertThat(network.edgesConnecting(N1, N2)).containsExactly(E12);
    assertTrue(networkAsMutableNetwork.removeEdge(E11));
    assertThat(network.edgesConnecting(N1, N1)).isEmpty();

    g1.putEdge(N1, N2);
    g1.putEdge(N3, N1);

    // for g2, add 3->1 first, then 1->2
    g2.putEdge(N3, N1);
    g2.putEdge(N1, N2);

    assertThat(g1).isEqualTo(g2);
  }

  @Test
  public void equivalent_edgeDirectionsDiffer() {
    graph.putEdge(N1, N2);

    MutableGraph<Integer> g2 = createGraph(edgeType);
    g2.putEdge(N2, N1);

    switch (edgeType) {

  public <N1 extends N, E1 extends E> MutableNetwork<N1, E1> build() {
    return new StandardMutableNetwork<>(this);
  }

  @SuppressWarnings("unchecked")
  private <N1 extends N, E1 extends E> NetworkBuilder<N1, E1> cast() {
    return (NetworkBuilder<N1, E1>) this;
  }

    addEdge(N1, N1, E11);
    assertThat(network.degree(N1)).isEqualTo(2);
    addEdge(N1, N2, E12);
    assertThat(network.degree(N1)).isEqualTo(3);
  }

  @Test
  public void inDegree_selfLoop() {
    assume().that(network.allowsSelfLoops()).isTrue();

    addEdge(N1, N1, E11);
    assertThat(network.inDegree(N1)).isEqualTo(1);
    addEdge(N4, N1, E41);
    assertThat(network.inDegree(N1)).isEqualTo(2);
  }

    putEdge(N1, N1);
    assertThat(graph.predecessors(N1)).containsExactly(N1);
    putEdge(N4, N1);
    assertThat(graph.predecessors(N1)).containsExactly(N1, N4);
  }

  @Test
  public void successors_selfLoop() {
    assume().that(graph.allowsSelfLoops()).isTrue();

    putEdge(N1, N1);
    assertThat(graph.successors(N1)).containsExactly(N1);
    putEdge(N1, N2);

   * Specifies the order of iteration for the elements of {@link Graph#nodes()}.
   *
   * <p>The default value is {@link ElementOrder#insertion() insertion order}.
   */
  public <N1 extends N> GraphBuilder<N1> nodeOrder(ElementOrder<N1> nodeOrder) {
    GraphBuilder<N1> newBuilder = cast();
    newBuilder.nodeOrder = checkNotNull(nodeOrder);
    return newBuilder;
  }

  /**

    directedGraph.putEdgeValue(N1, N1, E11);
    directedGraph.putEdgeValue(N3, N4, E34);

    MutableValueGraph<Integer, String> expectedTranspose =
        ValueGraphBuilder.directed().allowsSelfLoops(true).build();
    expectedTranspose.putEdgeValue(N3, N1, E13);
    expectedTranspose.putEdgeValue(N1, N3, E31);
    expectedTranspose.putEdgeValue(N2, N1, E12);
    expectedTranspose.putEdgeValue(N1, N1, E11);

    directedGraph.putEdge(N1, N2);
    containsExactlySanityCheck(edges, EndpointPair.ordered(N1, N2));

    directedGraph.putEdge(N2, N1);
    containsExactlySanityCheck(edges, EndpointPair.ordered(N1, N2), EndpointPair.ordered(N2, N1));

    directedGraph.removeEdge(N1, N2);
    directedGraph.removeEdge(N2, N1);
    containsExactlySanityCheck(edges);

    assertThrows(