@Override
    public void postMergeRegionsCommitAction(
      final ObserverContext<MasterCoprocessorEnvironment> ctx, final RegionInfo[] regionsToMerge,
      final RegionInfo mergedRegion) throws IOException {
      latch.countDown();
      throw new IOException("this procedure will fail at here forever");
    }
Class to test HBaseHbck. Spins up the minicluster once at test start and then takes it down
afterward. Add any testing of HBaseHbck functionality here.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestHbck.java