public void run() {
          try {
            // use the updated memstoreScanners and pass it to updateReaders
            scan.updateReaders(true, Collections.emptyList(), memScanners);
          } catch (IOException e) {
            e.printStackTrace();
          }
        }
This test tests whether parallel {@link StoreScanner#close()} and
{@link StoreScanner#updateReaders(List, List)} works perfectly ensuring that there are no
references on the existing Storescanner readers.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestStoreScannerClosure.java