testing rememberAnsweringNavigator result handling in a Presenter test

[frett]

I'm trying to figure out a way to test handling of a PopResult returned to an Answering Navigator in my presenter. From what I can tell the rememberAnsweringNavigator composable relies on a LocalBackStack composition local that isn't set within a presenter test.

Sample logic:

class Presenter(val navigator: Navigator) :CircuitUiPresenter {
  fun present(): State {
    val answeringNavigator = rememberAnsweringNavigator<OtherScreen.Result>(navigator) {
      // logic to be tested
    }
    
    return State(
      launchOtherScreen = {
        answerNavigator.goTo(OtherScreen)
      }
    )
  }
}

@Test
fun presenterTest = runTest {
  val navigator = FakeNavigator()
  
  Presenter(navigator).test {
    awaitItem().launchOtherScreen()
    
    // how do I trigger a OtherScreen.Result to test the result handling logic?
  }
}

[stagg]

Think this gets really close to being an integration test as it's verifying the interaction between the two screens?

Should be able to setup a test using createComposeRule where you can then set a NavigableCircuitContent to test. Will look into adding a compose test doing that, as it gets a bit awkward when done as a unit test:

    presenterTestOf({
      withCompositionLocalProvider(LocalBackStack provides backstack) { presenter.present() }
    }) {

[frett]

The screen has a public type safe response defined via the PopResult. So it'd be nice to not have to go through an integration test to generate a sample response.

The LocalBackStack composition local is currently internal, and CompositionLocalProvider returns Unit, so unfortunately it's not possible to wrap the test in a composition local and still test the output of presenter.present() anyways.

My current solution I came up with after this post was to use mockposable to capture the callback from rememberAnsweringNavigator and then manually trigger the callback as necessary. Not an ideal clean solution, but currently workable.

[frett]

oh, withCompositionLocalProvider is an internal circuit method that solves the presenter.present() return value problem

[stagg]

Added a sample compose test for this with #1582.
It's testing the presenter in a headless fashion by capturing the states. Allows for interacting with the presenter across the navigation boundary in an integrated fashion.

[frett]

Thanks for the example, I was able to repurpose the concepts into my existing tests