swift-composable-architecture-mirror/Tests/ComposableArchitectureTests/TestStoreTests.swift

import Combine
import ComposableArchitecture
import XCTest

class TestStoreTests: XCTestCase {
  func testEffectConcatenation() {
    struct State: Equatable {}

    enum Action: Equatable {
      case a, b1, b2, b3, c1, c2, c3, d
    }

    let testScheduler = DispatchQueue.testScheduler

    let reducer = Reducer<State, Action, AnySchedulerOf<DispatchQueue>> { _, action, scheduler in
      switch action {
      case .a:
        return .merge(
          Effect.concatenate(.init(value: .b1), .init(value: .c1))
            .delay(for: 1, scheduler: scheduler)
            .eraseToEffect(),
          Empty(completeImmediately: false)
            .eraseToEffect()
            .cancellable(id: 1)
        )
      case .b1:
        return
          Effect
          .concatenate(.init(value: .b2), .init(value: .b3))
      case .c1:
        return
          Effect
          .concatenate(.init(value: .c2), .init(value: .c3))
      case .b2, .b3, .c2, .c3:
        return .none

      case .d:
        return .cancel(id: 1)
      }
    }

    let store = TestStore(
      initialState: State(),
      reducer: reducer,
      environment: testScheduler.eraseToAnyScheduler()
    )

    store.assert(
      .send(.a),

      .do { testScheduler.advance(by: 1) },

      .receive(.b1),
      .receive(.b2),
      .receive(.b3),

      .receive(.c1),
      .receive(.c2),
      .receive(.c3),

      .send(.d)
    )
  }
}