private void generateHFiles() throws IOException {
    for (int i = 0; i < 4; i++) {
      long ts = EnvironmentEdgeManager.currentTime();
      for (int j = 0; j < 5; j++) {
        byte[] row = Bytes.toBytes(j);
        region.put(new Put(row).addColumn(FAMILY, QUAL, ts, Bytes.toBytes(i * 10 + j)));
        region.delete(new Delete(row).addFamilyVersion(FAMILY, ts));
      }

      for (int j = 5; j < 10; j++) {
        byte[] row = Bytes.toBytes(j);
        region.put(new Put(row).addColumn(FAMILY, QUAL, ts + 1, Bytes.toBytes(i * 10 + j)));
      }

      FlushResult result = region.flush(true);
      if (
        result.getResult() == FlushResult.Result.CANNOT_FLUSH
          || result.getResult() == FlushResult.Result.CANNOT_FLUSH_MEMSTORE_EMPTY
      ) {
        throw new IOException("Can not flush region, flush result: " + result);
      }
    }
  }
A UT to make sure that everything is fine when we fail to load bloom filter.
<p>
See HBASE-27936 for more details.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestBloomFilterFaulty.java