Bug: callOriginal() for default interface methods is not working about mockk

[rafalwrzeszcz]

This is a HUGE blocker, making testing default functions if not impossible then at least horribly complex instead of straight-forward. It was reported over 3 years ago and not even a feedback available here. What the …?

[zakhenry]

quick update, a much cleaner option works with abstract classes:

import io.mockk.*

data class ItemData(val id: Int)

interface Database {
    fun insertItems(items: List<ItemData>)
    fun deleteItems(items: List<ItemData>)
    fun runTransaction(alsoDelete: Boolean) {
        insertItems(listOf(ItemData(id = 1), ItemData(id = 2), ItemData(id = 3)))
        if (alsoDelete)
            deleteItems(listOf(ItemData(id = 4), ItemData(id = 5), ItemData(id = 6)))
    }
}


fun main(args: Array<String>) {
//    val x = mockk<Database>() // this should work, but doesn't due to https://github.com/mockk/mockk/issues/64

    // instead we create an abstract class to work around the issue.
    abstract class DatabaseMock: Database
    val x = mockk<DatabaseMock>()
    
    // the members/methods of the interface need to be stubbed too:
    every { x.insertItems(any()) } just Runs
    every { x.deleteItems(any()) } just Runs

    every { x.runTransaction(any()) } answers { callOriginal() }
    x.runTransaction(alsoDelete = true)
    verify { x.insertItems(listOf(ItemData(id = 1), ItemData(id = 2), ItemData(id = 3))) }
}

[ondrej-simon]

This is a problem caused by Mockk not being able to reliably spy interfaces. The solution I am using is also by creating an in-place abstract class "implementing" the interface I want to test, but instead of mockk-ing it, I use spyk call on the abstract class, that way i do not need to declare the callOriginal() on methods I want to actually test.

[aivinog1]

Hello everyone! I was encountered with this too and I wish to fix it :) So, I can start to fix it but are there any clues or advice about it?

[flapenna]

@flapenna : Is this issue fixed by above PR?

It should, but the fix hasn't been released yet

[Raibaz]

Sorry about the delay in the release, planning to make one next week.

[fargus9]

This is blocking some of my tests as well...

[jsingle]

Same here

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If you are sure that this issue is important and should not be marked as stale just put an important tag.

[munnitz]

What's the status on this one? I tried using this when mocking an interface like so

class InterfaceMock : Interface by mockk() {
    init {
        coEvery { defaultSuspendFunctionCall(any()) } coAnswers { callOriginal() }
    }
}

but it does not seem to work. Am I using it incorrectly or is it still not fixed?

[juniofernandes-hotmart]

Same issue here. Any feedbacks?

[dugsmith]

I'm also blocked writing a test like this because of this problem. Any plans to fix it?

[zakhenry]

I've banged my head against this for a while and found an workaround. Annoying but workable in the interim:

import io.mockk.*

data class ItemData(val id: Int)

interface Database {
    fun insertItems(items: List<ItemData>)
    fun deleteItems(items: List<ItemData>)
    fun runTransaction(alsoDelete: Boolean) {
        insertItems(listOf(ItemData(id = 1), ItemData(id = 2), ItemData(id = 3)))
        if (alsoDelete)
            deleteItems(listOf(ItemData(id = 4), ItemData(id = 5), ItemData(id = 6)))
    }
}


fun main(args: Array<String>) {
//    val x = mockk<Database>() // this should work, but doesn't due to https://github.com/mockk/mockk/issues/64

    // instead we create an anonymous object that implements the interface (but doesn't actually implement it; we stub the methods)
    val x = spyk(object: Database {
        override fun deleteItems(items: List<ItemData>) {}
        override fun insertItems(items: List<ItemData>) {}
    })
    // the members/methods of the interface can be stubbed if needed: 
//    every { x.insertItems(any()) } just Runs
//    every { x.deleteItems(any()) } just Runs

    every { x.runTransaction(any()) } answers { callOriginal() }
    x.runTransaction(alsoDelete = true)
    verify { x.insertItems(listOf(ItemData(id = 1), ItemData(id = 2), ItemData(id = 3))) }
}

[levinotik]

Ran into this as well today. I resolved with @zakhenry's workaround, but it'd be great if this could be fixed. Makes tests a bit ugly and confusing for others when they see this empty abstract class sitting there.

[goro-7]

@flapenna : Is this issue fixed by above PR?