@Override
    public StoreStats getStoreStats() {
      isCollected = true;
      getStatsCountdown.countDown();
      return storeStats;
    }
Mocked {@link Store} that is intended to return a predefined {@link StoreStats} when getStoreStats is called.
ambry-server/src/test/java/com/github/ambry/server/StatsManagerTest.java