}

  @Test
  public void forGraph_depthFirstPreOrder_diamond() {
    Traverser<Character> traverser = Traverser.forGraph(DIAMOND_GRAPH);
    assertEqualCharNodes(traverser.depthFirstPreOrder('a'), "abdc");
    assertEqualCharNodes(traverser.depthFirstPreOrder('b'), "bd");
    assertEqualCharNodes(traverser.depthFirstPreOrder('c'), "cd");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "d");
  }

  @Test

  }

  @Test
  public void forGraph_depthFirstPreOrder_diamond() {
    Traverser<Character> traverser = Traverser.forGraph(DIAMOND_GRAPH);
    assertEqualCharNodes(traverser.depthFirstPreOrder('a'), "abdc");
    assertEqualCharNodes(traverser.depthFirstPreOrder('b'), "bd");
    assertEqualCharNodes(traverser.depthFirstPreOrder('c'), "cd");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "d");
  }

  @Test

   *     Traverser.forGraph(graph).depthFirstPreOrder(node), maxNumberOfNodes);
   * }</pre>
   *
   * <p>See <a href="https://en.wikipedia.org/wiki/Depth-first_search">Wikipedia</a> for more info.
   *
   * @throws IllegalArgumentException if {@code startNode} is not an element of the graph
   */
  public final Iterable<N> depthFirstPreOrder(N startNode) {
    return depthFirstPreOrder(ImmutableSet.of(startNode));
  }

   * 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
   */