assertThat(graph.nodeOrder().comparator()).isEqualTo(comparator);
    assertThat(graph.nodes()).containsExactly(node1, node3, node5, node7).inOrder();
  }

  @Test
  public void customComparable() {
    MutableGraph<ComparableSubClass> graph =
        GraphBuilder.undirected().nodeOrder(ElementOrder.<ComparableSubClass>natural()).build();

    ComparableSubClass node2 = new ComparableSubClass(2);