*     unless it is constrained by using a method like {@link #nodeOrder}, or the builder is
 *     constructed based on an existing {@code Network} using {@link #from(Network)}.
 * @param <E> The most general edge type this builder will support. This is normally {@code Object}
 *     unless it is constrained by using a method like {@link #edgeOrder}, or the builder is

      char node1 = edge.charAt(0);
      char node2 = edge.charAt(1);
      graphMapBuilder.put(node1, node2);
      if (!directed) {
        graphMapBuilder.put(node2, node1);
      }
    }
    final ImmutableMultimap<Character, Character> graphMap = graphMapBuilder.build();

    return new SuccessorsFunction<Character>() {
      @Override

 *       locks---to each of the acquired locks, an edge from the soon-to-be-acquired lock is either
 *       verified or created.
 *   <li>If a new edge needs to be created, the outgoing edges of the acquired locks are traversed
 *       to check for a cycle that reaches the lock to be acquired. If no cycle is detected, a new
 *       "safe" edge is created.
 *   <li>If a cycle is detected, an "unsafe" (cyclic) edge is created to represent a potential

    // may change and break assumptions in this test [*]. This is not a bug in the implementation of
    // Ascii.equalsIgnoreCase(), but it is a signal that its documentation may need updating as
    // regards edge cases.

    // The Unicode point {@code 00df} is the lowercase form of sharp-S (ß), whose uppercase is "SS".
    assertEquals("PASSWORD", "pa\u00dfword".toUpperCase()); // [*]

      Collections.shuffle(edgeList, gen);
      int numEdgesToRemove = gen.nextInt(NUM_EDGES);
      for (int i = 0; i < numEdgesToRemove; ++i) {
        Object edge = edgeList.get(i);
        assertThat(network.removeEdge(edge)).isTrue();
      }

      assertThat(network.nodes()).hasSize(NUM_NODES);
      assertThat(network.edges()).hasSize(NUM_EDGES - numEdgesToRemove);

      return network.outEdges(node);
    }

    @Override
    public EndpointPair<N> incidentNodes(E edge) {
      return network.incidentNodes(edge);
    }

    @Override
    public Set<E> adjacentEdges(E edge) {
      return network.adjacentEdges(edge);
    }

    // _don't_ override edge*Connecting*; we want the behavior from AbstractNetwork
  }

    putEdge(N1, N2);
    assertThat(graph.predecessors(N2)).containsExactly(N1);
    // Edge direction handled correctly
    assertThat(graph.predecessors(N1)).isEmpty();
  }

  @Test
  public void successors_oneEdge() {
    putEdge(N1, N2);
    assertThat(graph.successors(N1)).containsExactly(N2);
    // Edge direction handled correctly
    assertThat(graph.successors(N2)).isEmpty();
  }

  @Test

    addNodes(graph);

    assertThat(graph.nodeOrder())
        .isEqualTo(ElementOrder.sorted(Ordering.<Integer>natural().reverse()));
    assertThat(graph.nodes()).containsExactly(4, 3, 1).inOrder();
  }

  // Edge order tests

  @Test
  public void edgeOrder_none() {
    MutableNetwork<Integer, String> network =
        NetworkBuilder.directed().edgeOrder(unordered()).build();

    putEdge(N1, N2);

    assertThat(graphAsMutableGraph.putEdge(N2, N1)).isFalse();
  }

  /**
   * Tests that the method {@code putEdge} will silently add the missing nodes to the graph, then
   * add the edge connecting them. We are not using the proxy methods here as we want to test {@code
   * putEdge} when the end-points are not elements of the graph.
   */
  @Test
  public void putEdge_nodesNotInGraph() {

    // Passed nodes should be in the correct edge direction, first is the
    // source node and the second is the target node
    assertThat(network.edgesConnecting(N2, N1)).isEmpty();
  }

  @Test
  public void inEdges_oneEdge() {
    addEdge(N1, N2, E12);
    assertThat(network.inEdges(N2)).containsExactly(E12);
    // Edge direction handled correctly
    assertThat(network.inEdges(N1)).isEmpty();