// View should be updated.
    assertThat(transpose.edgeValueOrDefault(N1, N2, null)).isEqualTo(E21);
    AbstractGraphTest.validateGraph(transpose.asGraph());
  }

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

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