Hi all I m having trouble with a unit test I m trying to val

Question

Hi all I m having trouble with a unit test I m trying to validate the behaviour of a StateFlow But the StateFlow is only in this particular state until a certain suspend function completes During testing my test double uses a delay to simulate a long running task But due to the nature of `runBlockingTest ` this delay is skipped so this function completes immediately and the StateFlow essentially bypasses the value I m trying to test It s worth mentioning I m using CashApp Turbine as well

Tim Malseed · Answer

```sealed class ViewState object None ViewState object Loading ViewState object Some ViewState class Foo val viewState = MutableStateFlow lt ViewState gt ViewState None fun updateViewState viewState value = ViewState Loading viewState value = someLongRunningOperation private suspend fun somePotentiallyLongRunningOperation ViewState delay 5000 return ViewState Some Test fun myTest = runBlockingTest foo viewState test foo updateViewState assertThat awaitItem isInstanceOf ViewState Loading class java Fails ViewState is ViewState Some cancelAndConsumeRemainingEvents ```

Eugen Martynov · Answer

coroutines 1 6 0

Eugen Martynov · Answer

I also use turbine from squire to test flows more nicely

Martin Rajniak · Answer

I wonder if this might be helpful gt Calls to `withContext ` `withContext Dispatchers Default ` and `withContext Dispatchers Main ` are common in coroutines based code bases Unfortunately just executing code in a test will not lead to these dispatchers using the virtual time source so delays will not be skipped in them So if I understand correctly if you use `withContext` and don t replace provider for the `TestDispatcher` then delay won t be skipped There has to be other way just that I noticed this so wanted to share slightly smiling face

Martin Rajniak · Answer

Also if you don t want to skip delays do you need to use `runBlockingTest` at all thinking face You might just want to create custom `CoroutineScope` as you would in production and run the test with that just thinking aloud not sure if true

Nick Allen · Answer

``` Test fun myTest = runBlockingTest launch foo updateViewState runCurrent assertEquals ViewState Loading fot viewState ```

Nick Allen · Answer

You need to run the tested code in a separate coroutine so you can control the clock and verify in the main body

Nick Allen · Answer

No a turbine user but I think this should work ``` Test fun myTest = runBlockingTest launch for updateViewState runCurrent foo viewState test assertThat awaitItem isInstanceOf ViewState Loading class java Fails ViewState is ViewState Some cancelAndConsumeRemainingEvents ```

Tim Malseed · Answer

Thanks all for the replies I ll have a look at these and see what works

Tim Malseed · Answer

None of the above seem to work so far I ve been working agains the actual production code so I ll try emulating this exact test I have a feeling Turbine is coming into play here as well

Tim Malseed · Answer

The above is psuedo code and I hadn t actually written that exact test Looks like it actually is working so perhaps there s some other problem in my production code I need to get better at actually writing small repros

Tim Malseed · Answer

Moving to `runTest ` does seem to solve most of my problems and revealed a few new ones that make me wonder how the tests ever passed at all