Mockito and asynchronous code

2014, Apr 28 One min read

On Friday, I talked about using Awaitility. It’s a good tool to black-box test asynchronous code. You trigger an action and then wait for a predicate to be true.

Another tool I use a lot to test asynchronous code is Mockito. People tend to forget that Mockito is able to verify calls on a mock with the same kind of polling mechanism as Awaitility.

Here’s a code sample:

@Test
public void async() {
  Receiver receiver = mock(Receiver.class);

  Sender sender = new Sender(receiver);
  sender.post("hello");

  verify(receiver, timeout(1000)).onMessage("hello");
}

Simple, yet very effective.

Also, remember that the easiest way to test asynchronous code is to make it synchronous!