swift - 模拟并注入(inject) ObservableObject

Question

我有一个类Foo对 ObservableObject 具有多个依赖项.出于测试目的，我想创建这些对象的模拟版本，但我看不到这样做的方法，然后将它们注入(inject) Foo .

我无法创建另一个协议(protocol)，我的 ObservableObject实现是因为 ObservableObject协议(protocol)具有自身或关联的类型要求，不能用作声明的类型和

我不能子类化 ObservableObject因为它有 @Published无法覆盖的属性包装成员。

Answer 1

目前我看到的唯一方法是编写一个订阅 ObservableObject 的模拟订阅者。 :

final class SomeState: ObservableObject {
  @Published var someValue: String?
}

如果 ObservableObject看起来像这样你可以像这样实现模拟订阅者(我称他们为 Watcher ):

final class SomeStateWatcher {
  let someState: SomeState

  var didSetSomeValue: Bool = false
  var lastSomeValue: String?

  private var someValueSubscriber: AnyCancellable?

  init(someState: SomeState) {
    self.someState = someState

    self.someValueSubscriber = self.someState.$someValue
      .sink(receiveValue: { value in 
        self.didSetSomeValue = true
        self.lastSomeValue = value
      })
  }
}

func testDoStuffThatChangesTheLocalSomeStateProperty() {
  someImplementation.doStuffThatChangesTheLocalSomeStateProperty(with: "Fourty2")

  XCTAssertTrue(someStateWatcher.didSetSomeValue, "It should have published someValue")
  XCTAssertEqual(someStateWatcher.lastSomeValue, "Fourty2", "It should have published the correct value)
}