private static HStoreFile createFile() throws Exception {
    HStoreFile sf = mock(HStoreFile.class);
    when(sf.getPath()).thenReturn(new Path("file"));
    StoreFileReader r = mock(StoreFileReader.class);
    when(r.length()).thenReturn(10L);
    when(sf.getReader()).thenReturn(r);
    return sf;
  }
Firstly write 10 cells (with different time stamp) to a qualifier and flush to hfile1, then
write 10 cells (with different time stamp) to the same qualifier and flush to hfile2. The
latest cell (cell-A) in hfile1 and the oldest cell (cell-B) in hfile2 are with the same time
stamp but different sequence id, and will get scanned successively during compaction.
<p/>
We set compaction.kv.max to 10 so compaction will scan 10 versions each round, meanwhile we set
keepSeqIdPeriod=0 in {@link DummyCompactor} so all 10 versions of hfile2 will be written out
with seqId cleaned (set to 0) including cell-B, then when scanner goes to cell-A it will cause
a scan out-of-order assertion error before HBASE-16931 if error occurs during the test
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestCompaction.java