* visit elements during a traversal once and only once.
   */
  @VisibleForTesting
  @CanIgnoreReturnValue
  @CheckForNull
  MoveDesc<E> removeAt(int index) {
    checkPositionIndex(index, size);
    modCount++;
    size--;
    if (size == index) {
      queue[size] = null;
      return null;
    }
    E actualLastElement = elementData(size);

   * visit elements during a traversal once and only once.
   */
  @VisibleForTesting
  @CanIgnoreReturnValue
  @CheckForNull
  MoveDesc<E> removeAt(int index) {
    checkPositionIndex(index, size);
    modCount++;
    size--;
    if (size == index) {
      queue[size] = null;
      return null;
    }
    E actualLastElement = elementData(size);

      if (value == 8) {
        iter.remove();
      }
    }
    assertIntact(q);
    assertThat(result).containsExactly(1, 15, 13, 8, 14);
  }

  /**
   * This tests a special case of the removeAt() call. Moving an element sideways on the heap could
   * break the invariants. Sometimes we need to bubble an element up instead of trickling down. See
   * implementation.
   */
  public void testInvalidatingRemove() {

      if (value == 8) {
        iter.remove();
      }
    }
    assertIntact(q);
    assertThat(result).containsExactly(1, 15, 13, 8, 14);
  }

  /**
   * This tests a special case of the removeAt() call. Moving an element sideways on the heap could
   * break the invariants. Sometimes we need to bubble an element up instead of trickling down. See
   * implementation.
   */
  public void testInvalidatingRemove() {

      }
    }

    // Removes the maximum node from this subtree to be reused elsewhere
    @CheckForNull
    private AvlNode<E> removeMax(AvlNode<E> node) {
      if (right == null) {
        return left;
      } else {
        right = right.removeMax(node);
        distinctElements--;
        totalCount -= node.elemCount;
        return rebalance();
      }
    }

      }
    }

    // Removes the maximum node from this subtree to be reused elsewhere
    @CheckForNull
    private AvlNode<E> removeMax(AvlNode<E> node) {
      if (right == null) {
        return left;
      } else {
        right = right.removeMax(node);
        distinctElements--;
        totalCount -= node.elemCount;
        return rebalance();
      }
    }