hi everybody, im using mockk for mocking the follo...

# announcements

[Andreas Unterweger]

hi everybody, im using mockk for mocking the following test fails on the second assertion (returned value is 1 instead of 2). why?

class Test {

    @test
    internal fun name() {
        val mock = mockk<Logic>()
        every { mock.doSth() } returns 2
        mock.doSth() shouldBe 2

        val obj = object : HasLogic {}
        obj.doSth() shouldBe 2
    }
}

interface HasLogic {
    fun doSth() = Logic.doSth()
}

object Logic {
    fun doSth() = 1
}

[wasyl]

You need to use triple backticks to format multiline code 🙂 ` ``` `

[Andreas Unterweger]

thx just fixed it

[wasyl]

Anyway it doesn’t work, because when you’re mocking Logic by doing val mock = mockk<Logic>() it’s only mock variable which, well, is a mock. mockk<Logic>() does not change the object Logic that you define

[Andreas Unterweger]

how can i mock all instances?

[wasyl]

and since HasLogic interface uses Logic object directly, and not your mock, it uses real implementation

[Andreas Unterweger]

im coming from jmockit and there this would work

[wasyl]

im coming from jmockit and there this would work

The difference is Logic.doSth is not a static method call — it’s a method declared on a Logic singleton instance. If you really need and want static methods, you should drop object Logic declaration whatsoever. Top-level functions are static jvm methods

[wasyl]

Maybe adding @JvmStatic would works as well, but I wouldn’t know. Either way you wouldn’t me mocking the entire Logic object, rather each function separately, I guess? Not really sure how to help here, since generally what you should do for testability is to inject the dependencies into the objects you’re testing

[Andreas Unterweger]

hmmm...i just tried @jvmstatic that gives a compilation error. i will further investigate but i assume there must be a solution, otherwise it would be a big drawback...anyways thank you

[Andreas Unterweger]

found the answer

class Test {

    @Test
    internal fun name() {
        mockkObject(Logic)
        every { Logic.doSth() } returns 2

        val obj = object : HasLogic {}
        obj.doSth() shouldBe 2
    }
}

interface HasLogic {
    fun doSth() = Logic.doSth()
}

object Logic {

    fun doSth() = 1
}

[wasyl]

Interesting. What would happen if you didn’t write val mock = mockkObject(Logic)?

[wasyl]

Anyway that makes sense if mockk library works like that. I’m not using so I wasn’t very helpful 😐

[Andreas Unterweger]

works without the val assignment too will fix it

[James Richardson]

So that's sorted out the how, but the why remains. You've just tested your mock implementation. Seems odd...

[James Richardson]

Usually mocks are handy for collaborators of a thing that's being tested not the implementation of it.

[Andreas Unterweger]

well, i guess its a corner case. if Logic.doSth() is an expensive operation, which is tested in its own unit test, i think it can make sense to only verify its called to save runtime