@Override
protected void init() {
final TriggerOneTime trigger = new TriggerOneTime();
final Join join = new Join();
trigger.setSucceedingOperator(new OperatorIDTuple(join, -1));
join.setPrecedingOperator(trigger);
subGraphMap = new HashMap<BasicOperator, String>();
subGraphMap.put(trigger, "trigger");
subGraphMap.put(join, "join");