Mockk: How to mock a return after a delay?

Question

I need to mock a call to some class and make it take some time.

The current code uses this:

every { useCase.execute(any()) } answers {
    AnswersWithDelay(50000, DoesNothing.doesNothing())
}

Now I am changing execute() to return an object of Notification class.

val notif = Notification(...)

But I can't figure out how to change this mock.

val answer: org.mockito.stubbing.Answer<Notification> = AdditionalAnswers.answer { invocation: InvocationOnMock -> notif }
val delayedAnswer = AdditionalAnswers.answersWithDelay(50000, { invocation: InvocationOnMock -> answer } )

I can't find how to make the answers { ... } compilable. Any tips?

Answer 1

The Mockito and MockK APIs are a bit confusing, because they share the terminology, but are not compatible. MockK's io.mockk.Answer is not compatible with Mockito's org.mockito.stubbing.Answer, and from there, all the other util classes do not match either.

So while originally it could have used DoesNothing.doesNothing(), because the return type was Unit/void, with a return type the mock must be created with MockK's idiomatic way.

So I resorted to:

    val answerF = FunctionAnswer { Thread.sleep(50000); notif }
    every { useCase.execute(any()) } .answers(answerF)