public void map(ImmutableBytesWritable key, Result value,
      OutputCollector<ImmutableBytesWritable, Put> output, Reporter reporter) throws IOException {
      output.collect(key, TestTableMapReduceBase.map(key, value));
    }
Pass the key, and reversed value to reduce
hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapred/TestTableMapReduce.java