assertThat(emptyGraph.allowsSelfLoops()).isTrue();
    assertThat(emptyGraph.nodeOrder()).isEqualTo(ElementOrder.<String>natural());
  }

  @Test
  public void immutableValueGraphBuilder_addNode() {
    ImmutableValueGraph<String, Integer> graph =
        ValueGraphBuilder.directed().<String, Integer>immutable().addNode("A").build();

    assertThat(graph.nodes()).containsExactly("A");