* {@link SuccessorsFunction#successors(Object)} can only be called for a subset of all nodes.
   */
  @Test
  public void forGraph_breadthFirst_iterableIsLazy() {
    RequestSavingGraph graph = new RequestSavingGraph(DIAMOND_GRAPH);
    Iterable<Character> result = Traverser.forGraph(graph).breadthFirst('a');

   * {@link SuccessorsFunction#successors(Object)} can only be called for a subset of all nodes.
   */
  @Test
  public void forGraph_breadthFirst_iterableIsLazy() {
    RequestSavingGraph graph = new RequestSavingGraph(DIAMOND_GRAPH);
    Iterable<Character> result = Traverser.forGraph(graph).breadthFirst('a');