如何在 MVC 中测试控制器类？

Question

我正在根据Model-View-Controller 模式在Swift 中构建一个简单的iOS 应用程序。我可以通过给它输入数据并根据我的期望断言输出结果来测试 Model 类。但我想知道如何测试 Controller 类？

看来如果我真的想测试Controller类，测试逻辑会复杂得多。是否有测试 Controller 类的标准方法？

Answer 1

不要测试您的UIViewControllers。有很多事情发生在他们身上，你看不到和/或无法控制。相反，在其他对象（例如视图模型）中保留尽可能多的逻辑，而不是您的 UIViewControllers。然后您可以测试您的视图模型，就像您测试您的模型一样。

编辑：

您可能希望如何构建 UIViewControllers 并测试模型和查看模型：

这段代码的主要内容是：

1. 使用Dependency Injection
2. 在 Release 中为类提供真实的依赖关系，在测试中为类提供虚假的依赖关系

视图控制器

// this class is super simple, so there's hardly any reason to test it now.
class SomeViewController: UIViewController {
    @IBOutlet weak var someLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        // we give the *real* user accessor in the view controller
        let viewModel = SomeViewModel(userAccessor: DBUserAccessor())
        someLabel.text = viewModel.welcomeMessage
    }
}

用户模型

struct User {
    var name: String
}

用户访问器

这是您的视图模型需要的一些依赖项。在发布期间提供一个真实的（在您的视图控制器中）。在测试的时候给一个假的，这样你就可以控制它了。

protocol UserAccessor {
    var currentUser: User? { get }
}

// since we're using the fake version of this class to test the view model, you might want to test this class on its own
// you would do that using the same principles that I've shown (dependency injection).
class DBUserAccessor: UserAccessor {
    var currentUser: User? {
        // some real implementation that's used in your app
        // get the user from the DB
        return User(name: "Samantha") // so not really this line, but something from CoreData, Realm, etc.
    }
}

class FakeUserAccessor: UserAccessor {
    // some fake implementation that's used in your tests
    // set it to whatever you want your tests to "see" as the current User from the "DB"
    var currentUser: User?
}

查看模型

这是您要测试的实际逻辑所在的位置。

class SomeViewModel {
    let userAccessor: UserAccessor

    init(userAccessor: UserAccessor) {
        self.userAccessor = userAccessor
    }

    var welcomeMessage: String {
        if let username = self.username {
            return "Welcome back, \(username)"
        } else {
            return "Hello there!"
        }
    }

    var username: String? {
        return userAccessor.currentUser?.name
    }
}

测试

最后，你想如何测试它。

class SomeViewModelTest: XCTestCase {
    func testWelcomeMessageWhenNotLoggedIn() {
        let userAccessor = FakeUserAccessor()
        let viewModel = SomeViewModel(userAccessor: userAccessor) // we give the *fake* user accessor to the view model in tests
        userAccessor.currentUser = nil // set the fake UserAccessor to not have a user "logged in"

        // assert that the view model, which uses whatever you gave it, gives the correct message
        XCTAssertEqual(viewModel.welcomeMessage, "Hello there!")
    }

    func testWelcomeMessageWhenLoggedIn() {
        let userAccessor = FakeUserAccessor()
        let viewModel = SomeViewModel(userAccessor: userAccessor)
        userAccessor.currentUser = User(name: "Joe") // this time, the use is "logged in"

        XCTAssertEqual(viewModel.welcomeMessage, "Welcome back, Joe") // and we get the correct message
    }
}