Testing isPresented

[jshier]

In addition to the well known dismiss dependency, there's also the less known isPresented, which indicates a presentation from a TCA context. Specifically, it's the value of dismiss.dismiss, the DismissEffect's closure. However, the only public init for DismissEffect only takes a non-optional closure, so there's no way to test isPresented = false, which we use to detect when our features originate without a TCA root, a common occurrence in a mixed TCA / UIKit codebase. How can we test this logic?

[stephencelis]

Can you share how you want to go about testing this? While testing it directly with overriding dismiss or isPresented might be convenient, we wonder if testing the integration would be better. E.g. maybe a TestStoreOf<Child> would exercise isPresented == false by default, but TestStoreOf<Parent> with a presented Child would exercise isPresented == true

[jshier]

This is specifically for the case where we're not in an existing TCA context, so that's not really a consideration we need.

I'm otherwise not sure, since I'm not sure what you'd otherwise consider to be "presented" in a test context, aside from the existence of a DismissEffect.

[wattson12]

Adding to this thread since I was searching with the same question today: we have a codebase we are about 80% migrated to TCA / SwiftUI but have some UIKit views still. In this case we have a TCA view which can be presented from either other TCA views or UIKit. When presented from TCA we call the bundled DismissEffect but when called from UIKit we call our own routing code

We have written the code to be something like

if isPresented { 
    return .run { _ in await dismiss() } 
else {
    return .run { _ in await ourOwnDismissFunction() }
}

But since we aren't sure how to make isPresented false in tests we can't test this flow (as written - we will likely rewrite to make our own dismiss function optional, and have an isPresentedFromUIKit type helper but would be nice to avoid code which is nearly duplicated from existing helpers)