private LinkedList<Pair<RegionInfo, RegionInfo>> getHoles(CatalogJanitor janitor,
    TableName tableName) throws IOException {
    janitor.scan();
    CatalogJanitorReport lastReport = janitor.getLastReport();
    assertFalse(lastReport.isEmpty());
    LinkedList<Pair<RegionInfo, RegionInfo>> holes = new LinkedList<>();
    for (Pair<RegionInfo, RegionInfo> hole : lastReport.getHoles()) {
      if (
        hole.getFirst().getTable().equals(tableName)
          || hole.getSecond().getTable().equals(tableName)
      ) {
        holes.add(hole);
      }
    }
    return holes;
  }
Take last byte and add one to it.
hbase-server/src/test/java/org/apache/hadoop/hbase/master/janitor/TestCatalogJanitorCluster.java