Hi! I'm rather new to working with coroutines and I have a question regarding testing them. I have a service similar to this

fun handleDelete(extIds: List<String>) {
        val ids = someClient1.getInternalIds(extIds) // get deleteable IDs

        try {
            runBlocking(<http://Dispatchers.IO|Dispatchers.IO>) { // use IO dispatcher as someClient2 makes a call to some remote service. 
                ids.forEach{ launch { someClient2.deleteId(it) } }
            }
        } catch (e: Exception) {
            handleException(e)
        }
    }

and I want to test it. My team uses Mockito and not Mockk, if that makes any difference. Maybe the test does not make sense, but as I am not very familiar with coroutines I want to test that these are run correctly in paralell and that they exit the runBlocking block after they're all done. So I was thinking of mocking the responses from

someClient2

so that say i have

extIds = listof("123", "456")

and the calls take respectively 500ms and 750ms, I want to check that in total this function does not use much more time than ~750ms and not (500+750)=1250ms. Is this possible using Mockito? And is it actually a useful test? 🤔

https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-test/#testing-launch-or-async-with-delay may be of use

Yeah, I saw this, but not sure how to use it in this scenario. All examples I see use a suspending function where they call delay, but how can I relate that to my function being a remote call? Also Mockito has a

ResponseWithDelay

or smth class, but that delay does not play nice with the timings in

runBlockingTest

it seems like

well, if you want to time it, this isn't really a suspend function, so it's actually out of coroutines land

Hmm, I could do as Jetbrains call it

extract function refactoring

and extract whats inside the launch into a suspending fcn, but yeah, then it is still only one function, and the paralell execution I want to test needs also the

forEach

to work, so that might not be a good idea anyway. Cool, I'll check that out now!