assertEquals(1, (int) mmHeap.pollLast());
    assertNull(mmHeap.peek());
    assertNull(mmHeap.peekLast());
    assertNull(mmHeap.pollLast());
  }

  public void testSmallMinHeap() {
    MinMaxPriorityQueue<Integer> mmHeap = MinMaxPriorityQueue.create();
    mmHeap.add(1);
    mmHeap.add(3);
    mmHeap.add(2);
    assertEquals(1, (int) mmHeap.peek());