How to use JUnit to test asynchronous processes

Question

How do you test methods that fire asynchronous processes with JUnit?

I don\'t know how to make my test wait for the process to end (it is not exactly a unit test, it

Answer 1

There are many answers here but a simple one is to just create a completed CompletableFuture and use it:

CompletableFuture.completedFuture("donzo")

So in my test:

this.exactly(2).of(mockEventHubClientWrapper).sendASync(with(any(LinkedList.class)));
this.will(returnValue(new CompletableFuture<>().completedFuture("donzo")));

I am just making sure all of this stuff gets called anyway. This technique works if you are using this code:

CompletableFuture.allOf(calls.toArray(new CompletableFuture[0])).join();

It will zip right through it as all the CompletableFutures are finished!