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() {

    PushObserver,
    Lockable {
    val events = mutableListOf<Any>()

    @Synchronized fun takeEvent(): Any {
      while (events.isEmpty()) {
        wait()
      }
      return events.removeAt(0)
    }

    @Synchronized override fun onRequest(
      streamId: Int,
      requestHeaders: List<Header>,
    ): Boolean {
      assertThat(streamId).isEqualTo(2)