private void flushRegion(WAL wal, byte[] regionEncodedName, Set<byte[]> flushedFamilyNames) {
    wal.startCacheFlush(regionEncodedName, flushedFamilyNames);
    wal.completeCacheFlush(regionEncodedName, HConstants.NO_SEQNUM);
  }
helper method to simulate region flush for a WAL.
hbase-server/src/test/java/org/apache/hadoop/hbase/wal/TestFSHLogProvider.java