public long openScanner(byte[] regionName, Scan scan) throws IOException {
    long scannerId = ThreadLocalRandom.current().nextLong();
    this.scannersAndOffsets.put(scannerId, new RegionNameAndIndex(regionName));
    return scannerId;
  }
Use this method to set what a scanner will reply as we next through
hbase-server/src/test/java/org/apache/hadoop/hbase/master/MockRegionServer.java