swift - 依赖注入(inject) : static methods and parameters

Question

我正在尝试向分层在 Objective-C 库上的 Swift 程序添加单元测试。我目前的主要问题是找到一种方法来注入(inject)使用参数化静态工厂方法创建的依赖项。

例如，以下代码是功能性的，但更耐测试:

class Processor {
    var service: RegistrationService?

    func register(user: String, pass: String) {
        let configuration = Configuration(user: user, pass: pass)
        service = RegistrationServiceProvider.registrationService(configuration: configuration)

        // Do various things with the 'service'
    }
}

请注意，RegistrationServiceProvider、RegistrationService 和Configuration 均来自 Objective-C 库。

我希望能够做的是提供在此代码中创建的 RegistrationService 作为默认值，并在测试时将其替换为我自己的模拟。如果没有 Configuration 对象，使用类似 http://www.danielhall.io/swift-y-dependency-injection-part-two 的东西会相当简单.

(我意识到我可以/应该将 Configuration 构造推送给调用者，但这并没有解决如何将它提供给默认服务的问题。)

欢迎提出建议和引用。

Answer 1

您可以创建 RegistrationService 和 RegistrationServiceProvider 的模拟并将它们注入(inject)测试，使用标准类型作为正常调用中的默认类型，如下面的代码(它包括您使用的类的示例版本和一些打印出来看看叫什么):

class Configuration {
    let user: String
    let pass: String

    init(user: String, pass: String) {
        self.user = user
        self.pass = pass
    }
}

class RegistrationService {
    let configuration: Configuration

    init(configuration: Configuration) {
        self.configuration = configuration
    }
}

class RegistrationServiceProvider {

    class func registrationService(configuration: Configuration) -> RegistrationService {
        print("Provider instantiated service")
        return RegistrationService(configuration: configuration)
    }
}

class Processor {
    var service: RegistrationService?
    func register(user: String, pass: String, serviceProvider: RegistrationServiceProvider.Type = RegistrationServiceProvider.self) {
        let configuration = Configuration(user: user, pass: pass)
        service = serviceProvider.registrationService(configuration: configuration)

        // Do various things with the 'service'
    }
}

class MockProvider: RegistrationServiceProvider {
    override class func registrationService(configuration: Configuration) -> RegistrationService {
        print("Mock provider instantiated mock service")
        return MockService(configuration: configuration)
    }
}

class MockService: RegistrationService {
    override init(configuration: Configuration) {
        super.init(configuration: configuration)
        print("Mock service initialized")
    }
}

let processor = Processor()

processor.register(user: "userName", pass: "myPassword") // Provider instantiated service

processor.register(user: "userName", pass: "myPassword", serviceProvider: MockProvider.self) // Mock provider instantiated mock service