Hey guys, I'm trying to do something with Orbit's ...

# orbit-mvi

[Benoît]

Hey guys, I'm trying to do something with Orbit's testing framework and basically the test finishes too early and so my assertion fails.

I'm trying to simulate an empty state in a Repository's Flow that should trigger a refresh, here's the code:

class MyContainerHost(
    scope: CoroutineScope,
    val repositoryFlow: Flow<String?>, // Flow representing repository state
    val requestRefresh: () -> Unit
) :
    ContainerHost<String, String> {
    override val container: Container<String, String> =
        scope.container("initial") {
            // When creating the container, listen for update on the Repository flow
            scope.launch {
                repositoryFlow.collect { newState ->
                    intent {
                        // When no state in flow, refresh it
                        if (newState != null) {
                            reduce { newState }
                        } else {
                            requestRefresh()
                        }
                    }
                }
            }
        }
}

The thing is when I write a unit test for that, the test returns before being able to get into my collect{} block.
How would you deal with that?

Thanks

[Benoît]

The test code:

val repositoryFlow = MutableStateFlow<String?>(null)
            val containerHost = MyContainerHost(
                this,
                repositoryFlow = repositoryFlow,
                requestRefresh = {
                    // This does not get called
                    repositoryFlow.tryEmit("refreshed state")
                }
            ).test("initial")

            containerHost.runOnCreate()

            containerHost.assert("initial") {
                states(
                    // This gives "expected states but never received"
                    { "refreshed state" }
                )
            }

[Mikolaj Leszczynski]

@Benoît I think the problem here is that you’re launching the flow collection from the raw origin scope - Orbit’s testing framework cannot handle coroutines launched outside of it’s own scope.

My suggestion would be to collect the flow within intent instead. No need for launching an extra new coroutine, as that’s what intent does anyway.

[Mikolaj Leszczynski]

please let me know if that works

[Mikolaj Leszczynski]

So something like:

class MyContainerHost(
    scope: CoroutineScope,
    val repositoryFlow: Flow<String?>, // Flow representing repository state
    val requestRefresh: () -> Unit
) :
    ContainerHost<String, String> {
    override val container: Container<String, String> =
        scope.container("initial") {
            // When creating the container, listen for update on the Repository flow
                intent {
                    repositoryFlow.collect { newState ->
                        // When no state in flow, refresh it
                        if (newState != null) {
                            reduce { newState }
                        } else {
                            requestRefresh()
                        }
                    }
                }
            }
        }
}

[Benoît]

Thanks Mikolaj, this doesn't work because the intent does not return (stuck doing collect) so the test gets stuck and eventually times out

[Mikolaj Leszczynski]

Tests that test ContainerHost using `Flow`s need special treatment.

There are a few options here I think.

1. Provide a finite flow as repositoryFlow
2. You can runOnCreate in your test in a launched coroutine so it doesn’t block your test
3. You can use liveTest

[Mikolaj Leszczynski]

I think 1) is the easiest and the most preferable here

[Mikolaj Leszczynski]

If your flow naturally completes, this intent will finish and the test can carry on.

[Mikolaj Leszczynski]

Let me know if that works!

[Benoît]

1. The problem with this approach is that I simplified the test for the example, but I'm actually testing a more complex feature that requires me to have a MutableStateFlow so I can send a bunch of stuff at different moment in time
2. This caused "expected states but never received", which makes sense, the runOnCreate doesn't get enough time to run before the assertion
3. What do you mean liveTest? How do I do that?

[Mikolaj Leszczynski]

So a bit of background:

The default suspending testing mode was developed to improve testing performance. It isolates the code under test (the invoked intent) from the rest of the framework and runs it within the test method as a simple suspending function.

However, you can also test using the real container as-is, with only one dispatcher swapped out (which you can override anyway).

Use ContainerHost.liveTest for this.

The assertions still work - they await for emissions from state and side effect flows with a timeout. So you can treat the rest of the test the same I think.

[Mikolaj Leszczynski]

I think in your case liveTest will work best @Benoît

[Mikolaj Leszczynski]

hope this helps

[Benoît]

Ah perfect! liveTest is what I needed this whole time, thanks a lot @Mikolaj Leszczynski!
Btw there's no mention of liveTest on https://orbit-mvi.org/Test/overview/, might be a good idea to add it

[Mikolaj Leszczynski]

Yes indeed, mea culpa 😅

[Rak]

does any of the above change with the new runTest?

[Benoît]

It shouldn't, although in my experience runTest isn't strictly equal to runBlocking, if a test passes with runBlocking you can't (always) simply change it to runTest and expect it to pass as well. Sometimes the order of execution can differ