currentHeapSize++;
      } else {
        /* remove either min or max */
        if (random.nextBoolean()) {
          removeMinFromReplica(replica, mmHeap.poll());
        } else {
          removeMaxFromReplica(replica, mmHeap.pollLast());
        }
        for (Integer v : replica.keySet()) {
          assertThat(mmHeap).contains(v);
        }
        assertIntact(mmHeap);
        currentHeapSize--;