@Override
  public CheckAndMutateResult preCheckAndMutate(
    ObserverContext<? extends RegionCoprocessorEnvironment> c, CheckAndMutate checkAndMutate,
    CheckAndMutateResult result) throws IOException {
    ctPreCheckAndMutate.incrementAndGet();
    return RegionObserver.super.preCheckAndMutate(c, checkAndMutate, result);
  }
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