*    /   / \
   *   b   e   g
   *  / \ / \ /
   * c   d   h
   * }</pre>
   */
  private static final SuccessorsFunction<Character> GRAPH_CONTAINING_TREE_AND_DIAMOND =
      createDirectedGraph("ab", "fe", "fg", "bc", "bd", "ed", "eh", "gh");

  @Test
  public void forGraph_breadthFirst_javadocExample_canBeIteratedMultipleTimes() {
    Iterable<Character> result = Traverser.forGraph(JAVADOC_GRAPH).breadthFirst('a');

   *    /   / \
   *   b   e   g
   *  / \ / \ /
   * c   d   h
   * }</pre>
   */
  private static final SuccessorsFunction<Character> GRAPH_CONTAINING_TREE_AND_DIAMOND =
      createDirectedGraph("ab", "fe", "fg", "bc", "bd", "ed", "eh", "gh");

  @Test
  public void forGraph_breadthFirst_javadocExample_canBeIteratedMultipleTimes() {
    Iterable<Character> result = Traverser.forGraph(JAVADOC_GRAPH).breadthFirst('a');