*   <li>(1) "no" and (2) "no", use {@link #forGraph(SuccessorsFunction)}.
 *   <li>(1) "yes" and (2) "yes", use {@link #forTree(SuccessorsFunction)}.
 *   <li>(1) "yes" and (2) "no", you can use either, but {@code forTree()} will be more efficient.
 *   <li>(1) "no" and (2) "yes", <b><i>neither will work</i></b>, but if you transform your node
 *       objects into a non-recursive form, you can use {@code forGraph()}.
 * </ul>
 *
 * @author Jens Nyman

    Iterable<Character> result = Traverser.forGraph(TWO_TREES).breadthFirst('a');

    assertEqualCharNodes(result, "ab");
  }

  @Test
  public void forGraph_breadthFirstIterable_twoTrees() {
    assertEqualCharNodes(Traverser.forGraph(TWO_TREES).breadthFirst(charactersOf("a")), "ab");
    assertEqualCharNodes(Traverser.forGraph(TWO_TREES).breadthFirst(charactersOf("ac")), "acbd");
  }

  @Test

   * strategy}.
   */
  private static <N> Iterable<N> getReachableNodes(
      Graph<N> graph, N node, TransitiveClosureSelfLoopStrategy strategy) {
    Traverser<N> traverser = Traverser.forGraph(graph);
    switch (strategy) {
      case ADD_SELF_LOOPS_ALWAYS: // always include 'node'
        return traverser.breadthFirst(node);
      case ADD_SELF_LOOPS_FOR_CYCLES: // include 'node' iff there's an incident cycle