Android Kotlin - 单元测试延迟协程，在延迟完成时调用 lambda 操作

Question

Ive been struggling with this for quite some time now, perhaps someone could help... I have this function in my class under test:

fun launchForegroundTimer(context: Context) {
        helper.log("AppRate", "[$TAG] Launching foreground count down [10 seconds]")
        timerJob = helper.launchActionInMillisWithBundle(Dispatchers.Main, TimeUnit.SECOND.toMillis(10), context, this::showGoodPopupIfAllowed)
}

So in that function, I first write to some log and then I call a coroutine function that expects a Dispatcher param, how long to wait before running the action, Any object that I would like to pass on to the action and the actual action function that is invoked when time has passed.

So in this case, the this::showGoodPopupIfAllowed which is a private method in the class, gets called when the 10,000 ms have passed. Here is that function:

private fun showGoodPopupIfAllowed(context: Context?) {
        if (isAllowedToShowAppRate()) {
            showGoodPopup(context)
        }
}

In that first if, there are a bunch of checks that occur before I can call showGoodPopup(context)

Now, here is the helper.launchActionInMillisWithBundle function:

fun <T> launchActionInMillisWithBundle(dispatcher: CoroutineContext, inMillis: Long, bundle: T, action: (T) -> Unit): Job = CoroutineScope(dispatcher).launchInMillisWithBundle(inMillis, bundle, action)

And here is the actual CoroutineScope extension function:

fun <T> CoroutineScope.launchInMillisWithBundle(inMillisFromNow: Long, bundle: T, action: (T) -> Unit) = this.launch {
    delay(inMillisFromNow)
    action(bundle)
}

What I am trying to achieve is a UnitTest that calls the launchForegroundTimer function, calls the helper function with the appropriate arguments and also continue through and call that lambda showGoodPopupIfAllowed function where I can also provide mocked behaviour to all the IF statments that occur in isAllowedToShowAppRate .

Currently my test stops right after the launchActionInMillisWithBundle is called and the test just ends. I assume there is no real call to any coroutine because I am mocking the helper class... not sure how to continue here.

I read a few interesting articles but none seems to resolve such state. My current test function looks like this:

    private val appRaterManagerHelperMock = mockkClass(AppRaterManagerHelper::class)
    private val timerJobMock = mockkClass(Job::class)
    private val contextMock = mockkClass(Context::class)

    @Test
    fun `launch foreground timer`() {
        every { appRaterManagerHelperMock.launchActionInMillisWithBundle(Dispatchers.Main, TimeUnit.SECOND.toMillis(10), contextMock, any()) } returns timerJobMock
        val appRaterManager = AppRaterManager(appRaterManagerHelperMock)
        appRaterManager.launchForegroundTimer(contextMock)

        verify(exactly = 1) { appRaterManagerHelperMock.log("AppRate", "[AppRaterManager] Launching foreground count down [10 seconds]") }
    }

I'm using mockk as my Mocking lib. AppRaterManager is the class under test

I'd like to also mention that, in theory I could have moved the coroutine invocation outside the class under test. So an external class like activity.onResume() could launch some sort of countdown and then call directly a function that checks showGoodPopupIfAllowed() . But currently, please assume that I do not have any way to change the calling code so the timer and coroutine should remain in the class under test domain.

Thank you!

Answer 1

Alright, I read a bit deeper into capturing/answers over at https://mockk.io/#capturing and saw there is a capture function. So I captured the lambda function in a slot which enables me invoke the lambda and then the actual code continues in the class under test. I can mock the rest of the behavior from there.

Here is my test function for this case (for anyone who gets stuck):

    @Test
    fun `launch foreground timer, not participating, not showing good popup`() {
        val slot = slot<(Context) -> Unit>()
        every { appRaterManagerHelperMock.launchActionInMillisWithBundle(Dispatchers.Main, TimeUnit.SECOND.toMillis(10), contextMock, capture(slot)) } answers {
            slot.captured.invoke(contextMock)
            timerJobMock
        }

        every { appRaterManagerHelperMock.isParticipating() } returns false

        val appRaterManager = AppRaterManager(appRaterManagerHelperMock)
        appRaterManager.launchForegroundTimer(contextMock)

        verify(exactly = 1) { appRaterManagerHelperMock.log("AppRate", "[AppRaterManager] Launching foreground count down [10 seconds]") }
        verify(exactly = 1) { appRaterManagerHelperMock.isParticipating() }
        verify(exactly = 0) { appRaterManagerHelperMock.showGoodPopup(contextMock, appRaterManager) }
    }

So what's left now is how to test the coroutine actually invokes the lambda after the provided delay time is up.