t.Errorf("unexpected bucket size: %#v", watchers.watchersBuckets)
	}
	watchers0 := watchers.popExpiredWatchersThreadUnsafe()
	if len(watchers0) != 0 {
		t.Errorf("unexpected bucket size: %#v", watchers0)
	}

	clock.Step(10 * time.Second)
	watchers1 := watchers.popExpiredWatchersThreadUnsafe()
	if len(watchers1) != 1 || len(watchers1[0]) != 1 {
		t.Errorf("unexpected bucket size: %v", watchers1)
	}

		bucketID = t.startBucketID
	}
	watchers := t.watchersBuckets[bucketID]
	t.watchersBuckets[bucketID] = append(watchers, w)
	return true
}

func (t *watcherBookmarkTimeBuckets) popExpiredWatchersThreadUnsafe() [][]*cacheWatcher {
	currentBucketID := int64(t.clock.Since(t.createTime) / time.Second)
	// There should be one or two elements in almost all cases
	expiredWatchers := make([][]*cacheWatcher, 0, 2)

			}
		}
	}()

	wg.Add(1)
	go func() {
		defer wg.Done()
		for {
			select {
			case <-stopCh:
				return
			default:
				cacher.Lock()
				cacher.bookmarkWatchers.popExpiredWatchersThreadUnsafe()
				cacher.Unlock()
			}
		}
	}()

	// wait for adding/removing watchers to end
	wg.Wait()

	if watchErr != nil {
		t.Fatal(watchErr)
	}