@Override
  public void prePrepareTimeStampForDeleteVersion(
    ObserverContext<? extends RegionCoprocessorEnvironment> e, Mutation delete, Cell cell,
    byte[] byteNow, Get get) throws IOException {
    ctPrePrepareDeleteTS.incrementAndGet();
  }
A sample region observer that tests the RegionObserver interface. It works with
TestRegionObserverInterface to provide the test case.
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/SimpleRegionObserver.java