Java – robolectric: the looper that runs the handler in my case

I have a very simple class. It has a handler. When it processes a message, it sends a new message again:

public class MyRepeatTask{
  …
  public void startTask() {
    // send message with delay 5 sec
    handler.sendMessageDelayed(handler.obtainMessage(…),5000);
  }

  Handler  handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            // I put a log for unit test
            System.out.println(“handling message …”);
            // send message with delay again
            handler.sendMessageDelayed(handler.obtainMessage(…),5000);
        }
  }
}

As shown above, when starttask () is called, the handler will start sending messages within 5 seconds Then, in the handlemessage () callback, the handler sends the message again with a delay of 5 seconds The purpose of this is to repeat certain tasks (such as system. Out. Println())

I use robolectric to test the above class:

@RunWith(RobolectricTestRunner.class)
public class MyRepeatTaskTest {
  @Test
  public void testStartTask() {
    MyRepeatTask task = new MyRepeatTask();
    task.startTask();

    // run looper of ‘handler’ in task
    ShadowLooper shadowLooper = Shadows.shadowOf(task.handler.getLooper());
    shadowLooper.runToEndOfTasks();

    // sleep for 30 seconds
    Thread.sleep(30 * 1000);
  }
}

I want to see system every five seconds out. Println() message "process message..." However, when I run the test, I only see a message in the terminal once

It seems that the looper of the handler runs only one task and then stops

If I'm right, how do I keep the bending needle running all the time in robolectric? If I'm wrong, why do I only see one log message?

==========Renew===========

I tried @ RDS's answer, and I replaced thread sleep(30 * 1000); By:

for (int i = 0; i < N; i++){
   shadowLooper.runToEndOfTasks();
}

Now I can see "process message..." n times However, the whole test did not simulate the delay Use handler Sendmessagedelayed (handler. Obtainmessage (...), 5000) when sending a message, I have a delay of 5 seconds. Does the robolectric framework not simulate this delayed message at all? How do I delay testing?

Solution

The problem is when you call runtoendoftasks(); There is only one task at this stage

You should call shadowlooper runToEndOfTasks(); Instead of letting the test thread sleep N calls to your handler n times