使用模拟数据测试 URLSession 委托

Question

我们有 2 个 URLSession 委托在其正文中使用自定义代码（未显示以使这篇文章更清晰）：

   public func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {}

  public func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
     if let error = error {
            //code here
        } else if let response = task.response as? HTTPURLResponse, var dataResponse = self.dataReceived {
            if (400...499).contains(response.statusCode) {
                //handle response here
            }
}

我们有一个 mockURLSession 类：

protocol URLSessionDataTaskProtocol {
    func resume()
}

protocol URLSessionProtocol {
    typealias DataTaskResult = (Data?, URLResponse?, Error?) -> Void

    func dataTask(with request: Request, completionHandler: @escaping DataTaskResult) -> URLSessionDataTaskProtocol
}

class MockURLSession: URLSessionProtocol {

    typealias DataTaskResult = (Data?, URLResponse?, Error?) -> Void
    var nextDataTask = MockURLSessionDataTask()
    var nextData: Data?
    var nextError: Error?

    private (set) var lastURL: URL?

    func successHttpURLResponse(request: Request) -> URLResponse {
        return HTTPURLResponse(url: request.url!, statusCode: 200, httpVersion: "HTTP/1.1", headerFields: nil)!
    }

    func wrongHttpURLResponse(request: Request, statusCode:Int) -> URLResponse {
        return HTTPURLResponse(url: request.url!, statusCode: statusCode, httpVersion: "HTTP/1.1", headerFields: nil)!
    }

    func dataTask(with request: Request, completionHandler: @escaping DataTaskResult) -> URLSessionDataTaskProtocol {
        lastURL = request.url
        nextDataTask.resume()
        completionHandler(nextData, successHttpURLResponse(request: request), nextError)
        return nextDataTask
    }

}

class MockURLSessionDataTask: URLSessionDataTaskProtocol {
    private (set) var resumeWasCalled = false

    func resume() {
        resumeWasCalled = true
    }
}

我们遇到的问题是我必须为来自模拟服务器的特定响应（例如 404）编写单元测试。通常我会这样写响应：

  let urlReponse = MockURLSession().wrongHttpURLResponse(request: self.urlRequest!, statusCode: 404)

我遇到的问题是，因为我们使用的是 URLSession 委托，所以我无法将 mockResponse 作为参数注入到函数中，除非它不会被调用。基于模拟响应测试 URLSession 委托的最佳方法是什么？

Answer 1

您可以在初始化MockURLSession 时注入模拟响应。

将以下内容添加到您的MockURLSession：

private var mockResponse: HTTPURLResponse?

init() { }
init(mockResponse: HTTPURLResponse) {
    self.mockResponse = mockResponse
}

修改模拟的dataTask 函数以使用模拟响应调用完成处理程序（如果您提供了它）：

if let mockResponse = mockResponse {
    completionHandler(nextData, mockResponse, nextError)
}
else {
    //default case is success
    completionHandler(nextData, successHttpURLResponse(request: request), nextError)
}

现在，当您想要测试错误响应时，请在创建模拟会话时注入它：

let mockResponse = HTTPURLResponse(url: self.urlRequest.url!, statusCode: 404, httpVersion: "HTTP/1.1", headerFields: nil)!
let mockURLSession = MockURLSession(mockResponse: mockResponse)

当dataTask 被调用时，将使用你的模拟响应：

mockURLSession.dataTask(with: self.urlRequest) { (data, response, error) in
    if let response = response as? HTTPURLResponse {
        print("Status Code: \(response.statusCode)") // "Status Code: 404"
    }
}