@Override
    public FSDataInputStream open(Path p, int bufferSize) throws IOException {
      FSDataInputStream orig = fs.open(p, bufferSize);
      FaultyInputStream faulty = new FaultyInputStream(orig);
      inStreams.add(new SoftReference<>(faulty));
      return faulty;
    }
Cluster test which starts a region server with a region, then removes the data from HDFS
underneath it, and ensures that errors are bubbled to the client.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestFSErrorsExposed.java