NetworkBuilder.undirected().<Integer, String>build());
    for (MutableNetwork<Integer, String> network : testNetworks) {
      network.addEdge(1, 2, "1-2");
      EndpointPair<Integer> endpointPair = network.incidentNodes("1-2");
      assertThrows(IllegalArgumentException.class, () -> endpointPair.adjacentNode(3));
    }
  }

  @Test
  public void testEquals() {
    EndpointPair<String> ordered = EndpointPair.ordered("a", "b");

  }

  @Override
  public Iterator<EndpointPair<N>> incidentEdgeIterator(N thisNode) {
    return Iterators.transform(
        adjacentNodeValues.keySet().iterator(),
        (N incidentNode) -> EndpointPair.unordered(thisNode, incidentNode));
  }

  @Override
  public @Nullable V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {