StringBuilder builder = new StringBuilder();
    for (Node t : iterable) {
      builder.append(t.value);
    }
    return builder.toString();
  }

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

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

    assertTrue(
        "Iterator content was " + builder + " but forEach content was " + forEachBuilder,
        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");