Snapshot Tests - Mock Store

[TiagoSantosSilva]

Hi folks,

I'm currently trying to add snapshot tests to one of my views. I'm having some issues with the effects that are triggered when the snapshot runs and the .onAppear/.task is called on the view.

My current structure is the following

View

struct HomeView: View {
    let store: StoreOf<HomeFeature>
    @ObservedObject var viewStore: ViewStoreOf<HomeFeature> 

    init(store: StoreOf<HomePageFeature>) {
        self.store = store
        viewStore = ViewStore(store)
}

var body: some View {
    Group {
        if let error = viewStore.state.error {
            ErrorView(...)
        } else {
            homeView
        }
    }
    .onAppear {
        viewStore.send(.onAppear)
    }
    .isLoading(viewStore.state.isLoading)
}

The isLoading modifier is a custom modifier we have to display a shimmering view to the user.

Store

struct HomeFeature: ReducerProtocol {
    enum Action: Equatable {
        case onAppear
        ...
        ...
    }

    struct State: Equatable {
        var isLoading: Bool = false
        var error: EquatableError?
    }

    var body: some ReducerProtocol<State, Action> {
        Reduce { state, action in

            let effect: EffectTask<Action>

            switch action {
            case .onAppear:
                state.isLoading = true
                
               (... some long running effect e.g: network call)
           }
     }
}

I'm then trying to run a snapshot test for when the State contains an error (and is not loading), it's currently like this:

func testErrorState() {
    let nsError = NSError(
            domain: "test",
            code: 0, userInfo: [
                NSLocalizedDescriptionKey: "Error message"
            ]
        )
    let error = EquatableError(nsError)
    let store = StoreOf<HomeFeature>(initialState: .init(error: error), reducer: HomeFeature())
    let sut = HomePageView(store: mockedStore(error: error))
        .frame(width: 390, height: 850)
    assertViewSnapshot(sut)
}

The issue, however, is that since .onAppear is called, I'm not being able to make it so that the error message is displayed since isLoading is being set to true and that has priority over the error.

Is there a way to make it so that either:

• The Store I'm initializing the HomeView with has no actions/its actions do nothing?
• The View I'm initializing/testing doesn't get onAppear triggered?

I've tried both using the withDependencies { ... } initializer so that my mocked service would return an error right away in order to try to achieve the error state that way but it also doesn't seem to work here.
Using .actionless seems to provide a Store that I'm not able to use on the initializer 😕.

Ha anyone faced a similar issue and was able to find a solution for it?

Thanks!

[mbrandonw]

You can create your store with no reducer to represent a completely inert store that does nothing when you send actions to it. That allows you to craft whatever you state you want and just hand it to the view.

This is how it can look:

let store = StoreOf<HomeFeature>(initialState: .init(error: error), reducer: EmptyReducer())

Or if you are using the newest version of TCA that allows specifying the reducer in a trailing builder closure:

let store = StoreOf<HomeFeature>(initialState: .init(error: error)) {
}

[TiagoSantosSilva]

Thanks for the help Brandon.

We're not using the newest version of TCA yet but the first solution worked like a charm.

Cheers!