@Override
    public void start(@SuppressWarnings("rawtypes") CoprocessorEnvironment ctx) throws IOException {
      this.postHookCalls = new AtomicInteger(0);
    }
Tests class that validates that "post" observer hook methods are only invoked when the operation
was successful.
hbase-server/src/test/java/org/apache/hadoop/hbase/master/procedure/TestMasterObserverPostCalls.java