@Before
  public void dropMinHistoryLevel() throws Exception {
    try {
      TestTxnDbUtil.executeUpdate(conf, "DROP TABLE MIN_HISTORY_LEVEL");
    } catch (Exception e) {
      if (e instanceof SQLException) {
        SQLException ex = (SQLException) e;
        if (ex.getSQLState().equalsIgnoreCase("42Y55")) {
          // It was already dropped
          return;
        }
      }
      throw e;
    }
  }
Test for cleaner to run when min_history_level is dropped and it has to fallback to not using the table.
HMS can seamlessly switch to the new functionality every time it tries to access the table and it is not there anymore.
This can help upgrade procedure, where the table can be dropped as the last step, after every HMS has been updated.
ql/src/test/org/apache/hadoop/hive/ql/txn/compactor/TestCleanerWithoutMinHistoryLevel.java