setDistinctValues(AbstractGraphBuilder.class, GRAPH_BUILDER_A, GRAPH_BUILDER_B);
    setDistinctValues(Graph.class, IMMUTABLE_GRAPH_A, IMMUTABLE_GRAPH_B);
    setDistinctValues(MutableNetwork.class, mutableNetworkA, mutableNetworkB);
    setDistinctValues(NetworkBuilder.class, NETWORK_BUILDER_A, NETWORK_BUILDER_B);
    setDistinctValues(Network.class, IMMUTABLE_NETWORK_A, IMMUTABLE_NETWORK_B);

    MutableNetwork<Integer, String> g2 = builder.build();

    // for ug1, add e12 first, then e12_a
    g1.addEdge(N1, N2, E12);
    g1.addEdge(N1, N2, E12_A);

    // for ug2, add e12_a first, then e12
    g2.addEdge(N1, N2, E12_A);
    g2.addEdge(N1, N2, E12);

    assertThat(g1).isEqualTo(g2);
  }

  @Test
  public void equivalent_edgeDirectionsDiffer() {

    for (TwoArg.Action first : TwoArg.Action.values()) {
      for (TwoArg.Action second : TwoArg.Action.values()) {
        TwoArg bar = new TwoArg(first, second);
        if (first.equals(TwoArg.Action.THROW_A_NPE) && second.equals(TwoArg.Action.THROW_A_NPE)) {
          verifyBarPass(method, bar); // require both params to throw NPE
        } else {
          verifyBarFail(method, bar);
        }
      }
    }
  }

          "f-_-o.cOM",
          "f--1.com",
          "f11-1.com",
          "www",
          "abc.a23",
          "biz.com.ua",
          "x",
          "fOo",
          "f--o",
          "f_a",
          "foo.net.us\uFF61ocm",
          "woo.com.",
          "8server.shop",
          "123.cn",
          "a" + DELTA + "b.com",
          ALMOST_TOO_MANY_LEVELS,
          ALMOST_TOO_LONG);

    network.addEdge(N1, N2, E12_A);
    network.addEdge(N2, N1, E21);
    if (edgeType == EdgeType.DIRECTED) {
      assertThat(networkForTest.edgesConnecting(N1, N2)).containsExactly(E12, E12_A);
      assertThat(networkForTest.edgesConnecting(N2, N1)).containsExactly(E21);
    } else {
      assertThat(networkForTest.edgesConnecting(N1, N2)).containsExactly(E12, E12_A, E21);

 * definition in <a
 * href="http://stat.ethz.ch/R-manual/R-devel/library/stats/html/quantile.html">R</a>, and it is
 * described by <a
 * href="http://en.wikipedia.org/wiki/Quantile#Estimating_the_quantiles_of_a_population">
 * wikipedia</a> as providing "Linear interpolation of the modes for the order statistics for the
 * uniform distribution on [0,1]."
 *
 * <h3>Handling of non-finite values</h3>
 *

  private static final Integer N3 = 3;
  private static final Integer N4 = 4;
  private static final String E11 = "1-1";
  private static final String E11_A = "1-1a";
  private static final String E12 = "1-2";
  private static final String E12_A = "1-2a";
  private static final String E12_B = "1-2b";
  private static final String E21 = "2-1";
  private static final String E13 = "1-3";

    MutableNetwork<Integer, String> g2 = builder.build();

    // for ug1, add e12 first, then e12_a
    g1.addEdge(N1, N2, E12);
    g1.addEdge(N1, N2, E12_A);

    // for ug2, add e12_a first, then e12
    g2.addEdge(N1, N2, E12_A);
    g2.addEdge(N1, N2, E12);

    assertThat(g1).isEqualTo(g2);
  }

  @Test
  public void equivalent_edgeDirectionsDiffer() {

    assume().that(network.allowsParallelEdges()).isTrue();

    assertTrue(networkAsMutableNetwork.addEdge(N1, N2, E12));
    assertTrue(networkAsMutableNetwork.addEdge(N1, N2, E12_A));
    assertThat(network.edgesConnecting(N1, N2)).containsExactly(E12, E12_A);
  }

  @Test
  public void addEdge_orderMismatch() {
    assume().that(graphIsMutable()).isTrue();

    EndpointPair<Integer> endpoints = EndpointPair.unordered(N1, N2);

    setDistinctValues(AbstractGraphBuilder.class, GRAPH_BUILDER_A, GRAPH_BUILDER_B);
    setDistinctValues(Graph.class, IMMUTABLE_GRAPH_A, IMMUTABLE_GRAPH_B);
    setDistinctValues(MutableNetwork.class, mutableNetworkA, mutableNetworkB);
    setDistinctValues(NetworkBuilder.class, NETWORK_BUILDER_A, NETWORK_BUILDER_B);
    setDistinctValues(Network.class, IMMUTABLE_NETWORK_A, IMMUTABLE_NETWORK_B);