Hello, what is the goody way to test a function that's consuming a channel ? My function looks like this :

suspend fun start(channel: ReceiveChannel<Event>) {
  launch(coroutineContext) {
    for (event in channel) {
      val view = // do something with each the event
      withContext(context = UI) {
        _evenementLiveData.value = view
      }
    }
  }
}

and my test looks like this :

@Test
fun testStart() = runBlocking {
  //given
  val channel = ConflatedChannel<Event>()
  val observer = mock<Observer<EvenementDetailView>>()
  presenter.evenementLiveData.observeForever(observer)

  val evenement = // create an event

  //when
  presenter.start(channel)
  channel.send(event)


  //then
  assertThat(presenter.evenementLiveData.value).isEqualTo(expectedView)
}

However, as my method start is launching a coroutine, the assertion in the UT is run before the consumption of the event sent into the channel. I tried to remove the

launch { }

inside the

start()

function, but without it, the runBlocking coroutine of the UT is suspended on

presenter.start()

because of the

for

loop inside the

start()

function. Am I doing something really wrong here in the

start()

function or is this a bad design that is hard to unit test or am I simply missing a point somewhere ? Thx

It looks wrong to just.call launch inside of suspend function without join

Thx @gildor, i removed the

launch

in the

suspend fun start()

function, and I wrapped the call to

start()

in the unit test with

launch(Unconfined)

and now it's working great

It does not actually consumes the channel since you use a regular for loop that doesn't close the channel like

consumeEach

or wrapping with

consume

would do