assertEqualCharNodes(traverser.depthFirstPreOrder('c'), "cdab");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "dabc");
  }

  @Test
  public void forGraph_depthFirstPreOrderIterable_cycle() {
    Traverser<Character> traverser = Traverser.forGraph(CYCLE_GRAPH);
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("a")), "abcd");

    assertEqualCharNodes(traverser.depthFirstPreOrder('c'), "cdab");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "dabc");
  }

  @Test
  public void forGraph_depthFirstPreOrderIterable_cycle() {
    Traverser<Character> traverser = Traverser.forGraph(CYCLE_GRAPH);
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("a")), "abcd");

   * is in progress or when the iterators generated by {@link #children} are advanced.
   *
   * @deprecated Use {@link com.google.common.graph.Traverser#depthFirstPreOrder} instead, which has
   *     the same behavior.
   */
  @Deprecated
  public final FluentIterable<T> preOrderTraversal(final T root) {
    checkNotNull(root);
    return new FluentIterable<T>() {

   * a directory, no exception will be thrown and the returned {@link Iterable} will contain a
   * single element: that file.
   *
   * <p>Example: {@code Files.fileTraverser().depthFirstPreOrder(new File("/"))} may return files
   * with the following paths: {@code ["/", "/etc", "/etc/config.txt", "/etc/fonts", "/home",
   * "/home/alice", ...]}
   *
   * @since 23.5
   */

   * a directory, no exception will be thrown and the returned {@link Iterable} will contain a
   * single element: that file.
   *
   * <p>Example: {@code Files.fileTraverser().depthFirstPreOrder(new File("/"))} may return files
   * with the following paths: {@code ["/", "/etc", "/etc/config.txt", "/etc/fonts", "/home",
   * "/home/alice", ...]}
   *
   * @since 23.5
   */

   * created by this traverser if an {@link IOException} is thrown by a call to {@link
   * #listFiles(Path)}.
   *
   * <p>Example: {@code MoreFiles.fileTraverser().depthFirstPreOrder(Paths.get("/"))} may return the
   * following paths: {@code ["/", "/etc", "/etc/config.txt", "/etc/fonts", "/home", "/home/alice",
   * ...]}
   *
   * @since 23.5
   */

   * created by this traverser if an {@link IOException} is thrown by a call to {@link
   * #listFiles(Path)}.
   *
   * <p>Example: {@code MoreFiles.fileTraverser().depthFirstPreOrder(Paths.get("/"))} may return the
   * following paths: {@code ["/", "/etc", "/etc/config.txt", "/etc/fonts", "/home", "/home/alice",
   * ...]}
   *
   * @since 23.5
   */