@Override
  public boolean preCheckAndPutAfterRowLock(
    ObserverContext<? extends RegionCoprocessorEnvironment> e, byte[] row, byte[] family,
    byte[] qualifier, CompareOperator compareOp, ByteArrayComparable comparator, Put put,
    boolean result) throws IOException {
    ctPreCheckAndPutAfterRowLock.incrementAndGet();
    return true;
  }
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