assertThat(copy).isEqualTo(directedGraph);
  }

  @Test
  public void copyOf_undirectedValueGraph() {
    ValueGraph<Integer, String> undirectedGraph = buildUndirectedValueGraph();

    ValueGraph<Integer, String> copy = copyOf(undirectedGraph);
    assertThat(copy).isEqualTo(undirectedGraph);
  }

  @Test
  public void copyOf_directedNetwork() {