@BeforeClass
  public static void setUp() throws Exception {
    CONF = TEST_UTIL.getConfiguration();
    cacheConf = new CacheConfig(CONF);
    fs = TEST_UTIL.getTestFileSystem();
    TableName tableName = TableName.valueOf("test");
    TableDescriptor tableDescriptor = TableDescriptorBuilder.newBuilder(tableName)
      .setColumnFamily(ColumnFamilyDescriptorBuilder.of(fam)).build();
    RegionInfo info = RegionInfoBuilder.newBuilder(tableName).build();
    Path path = TEST_UTIL.getDataTestDir("test");
    region = HBaseTestingUtil.createRegionAndWAL(info, path, TEST_UTIL.getConfiguration(),
      tableDescriptor);
  }
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