public HRegionServer getRegionServer(ServerName serverName) {
    return hbaseCluster.getRegionServers().stream().map(t -> t.getRegionServer())
      .filter(r -> r.getServerName().equals(serverName)).findFirst().orElse(null);
  }
Grab a numbered region server of your choice.
@return region server
hbase-testing-util/src/main/java/org/apache/hadoop/hbase/MiniHBaseCluster.java