Graph<Integer> undirectedGraph = buildUndirectedGraph();

    Graph<Integer> copy = copyOf(undirectedGraph);
    assertThat(copy).isEqualTo(undirectedGraph);
  }

  @Test
  public void copyOf_directedValueGraph() {
    ValueGraph<Integer, String> directedGraph = buildDirectedValueGraph();

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

  @Test