assertThat(network.nodeOrder()).isEqualTo(unordered());
    assertThat(network.nodes()).containsExactly(4, 1, 3);
  }

  // Sorting of user-defined classes

  @Test
  public void customComparator() {
    Comparator<NonComparableSuperClass> comparator =
        (left, right) -> left.value.compareTo(right.value);

    MutableGraph<NonComparableSuperClass> graph =