How to test a method using sleep() with Java?

Question

I have the following method and I am struggling to get 100% code coverage.

public final class SleepingHelper {
    public static void sleepInMillis(Duration timeOfNextTry) {
        try {
            Thread.sleep(timeOfNextTry.toMillis());
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

The question is how can I force Thread.sleep to throw an exception?

Edit: since it was marked as duplicate, I am still wondering what I would assert in the test ? The other question Is more generic.

Answer 1

You need to interrupt it from another thread. For example:

 Thread t = new Thread() {
     public void run () {
        SleeperMillis.sleepInMillis(new Duration(10000000l));
     }
 }.start();
 Thread.sleep(100); // let the other thread start
 t.interrupt;