@Override
  public long getLogSegmentSize(LogSegmentName name) {
    if (logSegmentSizes.containsKey(name)) {
      return logSegmentSizes.get(name);
    } else {
      return 0;
    }
  }
Mock {@link BlobStoreStats} for test purposes
ambry-store/src/test/java/com/github/ambry/store/CompactionPolicyTest.java