@Override
  public void postFlush(ObserverContext<? extends RegionCoprocessorEnvironment> c, Store store,
    StoreFile resultFile, FlushLifeCycleTracker tracker) throws IOException {
    ctPostFlush.incrementAndGet();
    if (throwOnPostFlush.get()) {
      throw new IOException("throwOnPostFlush is true in postFlush");
    }
  }
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