@Override
    public String getClusterId() {
      return null;
    }
Connection class to use in {@link #testNonSuccessiveSplitsAreNotMerged}. This class returns
mocked {@link Table}, {@link RegionLocator}, {@link RegionSizeCalculator}, and {@link Admin}.
hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapreduce/TestTableInputFormatBase.java