it.next();
    it.next();
    mmHeap.remove(4);
    assertThrows(ConcurrentModificationException.class, () -> it.next());
  }

  /** Tests a failure caused by fix to childless uncle issue. */
  public void testIteratorRegressionChildlessUncle() {
    ArrayList<Integer> initial = Lists.newArrayList(1, 15, 13, 8, 9, 10, 11, 14);
    MinMaxPriorityQueue<Integer> q = MinMaxPriorityQueue.create(initial);