builder.toString().contentEquals(forEachBuilder));
    return builder.toString();
  }

  public void testPreOrder() {
    assertThat(iterationOrder(ADAPTER.preOrderTraversal(h))).isEqualTo("hdabcegf");
  }

  public void testPostOrder() {
    assertThat(iterationOrder(ADAPTER.postOrderTraversal(h))).isEqualTo("abcdefgh");
  }

  public void testBreadthOrder() {

 *
 * <pre>{@code
 *        h
 *      / | \
 *     /  e  \
 *    d       g
 *   /|\      |
 *  / | \     f
 * a  b  c
 * }</pre>
 *
 * <p>can be iterated over in preorder (hdabcegf), postorder (abcdefgh), or breadth-first order
 * (hdegabcf).
 *
 * <p>Null nodes are strictly forbidden.
 *
 * <p>Because this is an abstract class, not an interface, you can't use a lambda expression to

  }

  @Test
  public void forGraph_depthFirstPreOrder_tree() throws Exception {
    Traverser<Character> traverser = Traverser.forGraph(TREE);

    assertEqualCharNodes(traverser.depthFirstPreOrder('h'), "hdabcegf");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "dabc");
    assertEqualCharNodes(traverser.depthFirstPreOrder('a'), "a");
  }

  @Test

  }

  @Test
  public void forGraph_depthFirstPreOrder_tree() throws Exception {
    Traverser<Character> traverser = Traverser.forGraph(TREE);

    assertEqualCharNodes(traverser.depthFirstPreOrder('h'), "hdabcegf");
    assertEqualCharNodes(traverser.depthFirstPreOrder('d'), "dabc");
    assertEqualCharNodes(traverser.depthFirstPreOrder('a'), "a");
  }

  @Test