private HStoreFile mockStoreFileWithLength(long length) {
    HStoreFile sf = mock(HStoreFile.class);
    StoreFileReader sfr = mock(StoreFileReader.class);
    when(sf.isHFile()).thenReturn(true);
    when(sf.getReader()).thenReturn(sfr);
    when(sfr.length()).thenReturn(length);
    return sf;
  }
This test is for HBASE-26494, test the {@link RefCnt} behaviors in {@link ImmutableMemStoreLAB}
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java