@Override
      public boolean evaluate() throws Exception {
        return UTIL.getMiniHBaseCluster().getLiveRegionServerThreads().stream()
          .map(RegionServerThread::getRegionServer).allMatch(HRegionServer::walRollRequestFinished);
      }
Base class for testing serial replication.
hbase-server/src/test/java/org/apache/hadoop/hbase/replication/SerialReplicationTestBase.java