@Override
    public StoreInfo get(List<? extends StoreKey> ids, EnumSet<StoreGetOptions> storeGetOptions) throws StoreException {
      throw new IllegalStateException("Not implemented");
    }
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