graph = ValueGraphBuilder.undirected().build();
    graph.putEdgeValue(1, 2, "A");
    assertThat(graph.edgeValue(EndpointPair.unordered(2, 1))).hasValue("A");
  }

  @Test
  public void edgeValue_undirected_mismatch() {
    graph = ValueGraphBuilder.undirected().build();
    graph.putEdgeValue(1, 2, "A");
    // Check that edgeValue() throws on each possible ordering of an ordered EndpointPair
    IllegalArgumentException e =