Test for adapting a progress handler to Effect.subject

test_run.swift

import Combine
import ComposableArchitecture
import ComposableArchitectureTestSupport
import XCTest

class MainViewTests: XCTestCase {
    func test_run() throws {
        // Setup
        struct State: Equatable {
            var busy = false
            var stage = Stage.idle
        }
        enum Action: Equatable {
            case runTapped
            case progressUpdate(Stage)
        }
        enum Stage: String { case idle, started, finished }
        func run(progress: (Stage) -> Void) {
            // simulate successive stages
            progress(.started)
            progress(.finished)
        }
        let runEffect = Effect<Stage>._subject { subject in
            run {
                subject.send($0)
                if $0 == .finished { subject.send(completion: .finished) }
            }
            return AnyCancellable {
                subject.send(completion: .finished)  // or error?
            }
        }
        let reducer = Reducer<State, Action, Void> { state, action, env in
            switch action {
                case .runTapped:
                    state.busy = true
                    return runEffect
                        .map(Action.progressUpdate)
                case .progressUpdate(let stage):
                    state.stage = stage
                    if stage == .finished { state.busy = false }
            }
            return .noop
        }
        let store = TestStore(initialState: State(),
                              reducer: reducer,
                              environment: ())
        // Test
        store.assert(
            .send(.runTapped) {
                $0.busy = true
            },
            .receive(.progressUpdate(.started)) {
                $0.stage = .started
            },
            .receive(.progressUpdate(.finished)) {
                $0.stage = .finished
                $0.busy = false
            }
        )
    }
}