Detect unnecessary stubbings

Mockito throws an exception when a function is stubbed and then not actually invoked.

This is particularly useful when doing TDD, or generally when writing tests first, because it allows to stub a function, have the test fail because it was not invoked, and then make it pass by implementing the invocation.

We could add a parameter to the mockk() function and the @MockK annotation, or a configuration flag to make it global, so that it works somewhat like this:

class Test {
    @MockK(detectUnnecessaryStubbing = true)
    private lateinit var collaborator: Collaborator

    private lateinit var service: Service

    @BeforeEach
    fun setup() {
        MockKAnnotations.init(this) // Perhaps this could be another good place to enable the "unnecessary stubbing detection mode"

        service = Service(collaborator)
    }

    @Test
    fun test() {
        every { collaborator.function() } returns "foo"

        service.anotherFunction() // Not executing collaborator.function in here will fail
    }
}

A potential issue I see in this is the case when there are two tests executing service.anotherFunction(), one stubbing and invoking collaborator.function() and one not stubbing nor invoking it.

We need to find a way to detect that it’s ok for the second test not to invoke collaborator.function() even if it was stubbed in another test.

[Raibaz]

Implemented in 1.12.4.

[xpepper]

Great, I’m willing to test a version of MockK with this new behaviour as soon as is available!