AdditionalAnswers Answer0 ?

Hey,

Firstly, thanks so much for mockito - probably my most liked and often use dependency, alongside junit and assertj, mockito is always in my “must haves” for any new project 😃

Feature Request:

Currently there are Answer1-Answer6 which can be passed to AdditionalAnswers.answer(…)

Would you be open to adding an Answer0 (and VoidAnswer0) ?

This would allow these uses cases

public interface MyInterface {
    String method();
}

Currently have to cast, and have unused “invocation” input:

@Test
void test() {
    MyInterface mock = mock(MyInterface.class);
    when(mock.method()).thenAnswer((Answer<String>) invocation -> "hello");
}

With Answer0:

@Test
void test() {
    MyInterface mock = mock(MyInterface.class);
    when(mock.method()).thenAnswer(answer(() -> "hello"));
}

Also then allows for method ref:

@Test
void test() {
    MyInterface mock = mock(MyInterface.class);
    when(mock.method()).thenAnswer(answer(this::theAnswer));
}

private String theAnswer() {
   System.out.println("we're in the answer!");
   return "something";
}

(obviously these examples are contrived, imagine there being something other than being a basic return)

Happy to make a contribution for this if it’s something you agree could be useful?

Maybe there’s already a helper method in Mockito for this and I’ve just not found it…

[goughy000]

@TimvdLippe Yes I think you maybe missed something.

thenReturn only allows me to pass a precalculated value, not a value calculated at time of invocation.

e.g.

AtomicInteger i = new AtomicInteger();
when(mock.method()).thenAnswer(answer(() -> i.incrementAndGet()));

the only way to do this currently is like

AtomicInteger i = new AtomicInteger();
when(mock.method()).thenAnswer((Answer<Integer>) invocation -> i.incrementAndGet());

my actual use case where I came across this was something (but not exactly) like this

// given
CountDownLatch latch = new CountDownLatch(2);
when(mock.method()).thenAnswer((Answer<Integer>) invocation -> { latch.countDown(); return 1; });

// when
sut.call();

// then
latch.await(); // waits for 2 invocations on mock
assert(...);

given the Answer1-6 already existed, I felt it would have been convenient to write this if Answer0 had existed as I have no need for the InvocationOnMock parameter nor any method params

when(mock.method()).thenAnswer(answer(() -> { latch.countDown(); return 1; }));

if method() was actual method(p) then I can already do this in mockito… so it seems weird I can’t do it when there are no params, don’t you think?

when(mock.method(anyInt())).thenAnswer(answer(i -> { latch.countDown(); return 1; }));

[goughy000]

when(mock.method()).thenAnswer(invocation -> i.incrementAndGet());

this doesn’t help with the method ref use case

I’ve added a helper method to my test class instead, thanks anyway for your consideration