TLDR: Anyone have any experience testing `flow.cat...

# flow

[Kevin Worth]

TLDR: Anyone have any experience testing flow.catch that can offer some pointers?

Given a StateFlow, how can I force my unit test to exercise my .catch? It appears the unit test framework is designed to suppress all `Exception`s other than those that the test is expecting (i.e. assertThrows). I don’t want to assert an exception is thrown, I want my flow.catch{ … } to catch it, but I believe the framework is catching it instead.

val uiState: StateFlow<UiState> = myRepository.myModels
    .map<List<MyModel>, UiState>(::Success)
    .catch {
        // TRYING TO OBSERVE THIS IN TEST
        emit(UiState.Error(it))
    }
    .stateIn(...)

Maybe I’ve gone in the entirely wrong direction?
_

EDIT: Looks like @Test(expected = Exception::class) is helpful to get passed “Suppressed: Exception”, but now I still have the issue of my .catch apparently not running because I don’t see an emit.

[Kevin Worth]

Test output includes the following in a bunch of stack traces:

Suppressed: java.lang.Exception: Simulated error

(because my FakeRepository is throwing Exception("Simulated error"))

[Kevin Worth]

Even after telling the test to expect the exception, I still have the issue of my .catch apparently not running because I don’t see an emit.

Anyone have any ideas?

[Kevin Worth]

…after continuing to look at this… for those playing along at home, I think this really does come down to the intricacies of testing. I believe the test framework is still catching the exception, and simply allowing things to continue at which point my flow.catch never gets the chance to catch it.

[prudhvi reddy]

Hey @Kevin Worth

You got any workarounds for this?