After configuring the Controller Services and enqueuing the necessary FlowFiles, the Processor can be triggered to run by calling the run method of TestRunner. If this method is called without any arguments, it will invoke any method in the Processor with an @OnScheduled annotation, call the Processor's onTrigger method once, and then run the @OnUnscheduled and finally @OnStopped methods.

If it is desirable to run several iterations of the onTrigger method before the other @OnUnscheduled and @OnStopped life-cycle events are triggered, the run(int) method can be used to specify now many iterations of onTrigger should be called.

There are times when we want to trigger the Processor to run but not trigger the @OnUnscheduled and @OnStopped life-cycle events. This is useful, for instance, to inspect the Processor's state before these events occur. This can be achieved using the run(int, boolean) and passing false as the second argument. After doing this, though, calling the @OnScheduled life-cycle methods could cause an issue. As a result, we can now run onTrigger again without causing these events to occur by using the run(int,boolean,boolean) version of the run method and passing false as the third argument.

If it is useful to test behavior that occurs with multiple threads, this can also be achieved by calling the setThreadCount method of TestRunner. The default is 1 thread. If using multiple threads, it is important to remember that the run call of TestRunner specifies how many times the Processor should be triggered, not the number of times that the Processor should be triggered per thread. So, if the thread count is set to 2 but run(1) is called, only a single thread will be used.