private static void rollbackAllTxns(boolean val, IDriver driver) {
    driver.getConf().setBoolVar(HiveConf.ConfVars.HIVE_TEST_MODE_ROLLBACK_TXN, val);
  }
Set to true to cause all transactions to be rolled back, until set back to false.
itests/hive-unit/src/test/java/org/apache/hadoop/hive/ql/txn/compactor/TestMmCompactorOnTez.java