Network<N, EndpointPair<N>> asNetwork = graph.asNetwork();
    // Don't call AbstractNetworkTest.validateNetwork(asNetwork).  Mutual recursion.
    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());

    Network<Integer, EndpointPair<Integer>> asNetwork = graph.asNetwork();
    AbstractNetworkTest.validateNetwork(asNetwork);
    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());

    Network<N, EndpointPair<N>> asNetwork = graph.asNetwork();
    // Don't call AbstractNetworkTest.validateNetwork(asNetwork).  Mutual recursion.
    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());

    Network<Integer, EndpointPair<Integer>> asNetwork = graph.asNetwork();
    AbstractNetworkTest.validateNetwork(asNetwork);
    assertThat(graph.nodes()).isEqualTo(asNetwork.nodes());
    assertThat(graph.edges()).hasSize(asNetwork.edges().size());
    assertThat(graph.nodeOrder()).isEqualTo(asNetwork.nodeOrder());
    assertThat(graph.isDirected()).isEqualTo(asNetwork.isDirected());

    }
    N nodeU = endpoints.nodeU();
    N nodeV = endpoints.nodeV();
    return nodes().contains(nodeU) && successors(nodeU).contains(nodeV);
  }

  @Override
  public Network<N, EndpointPair<N>> asNetwork() {
    return new AbstractNetwork<N, EndpointPair<N>>() {
      @Override
      public Set<N> nodes() {
        return AbstractBaseGraph.this.nodes();
      }

      @Override