我将开发从一个简单的 Get 请求到为组合模拟 .dataTaskPublisher 以及最后一部分测试调用的步骤。这是一个随时可用的代码，供所有人使用，以防其他人需要它。
按照评论添加您的模型或任何取决于您的项目数据的内容。
所以这是为我的 NetworkRequest 类提供规则的协议：
protocol NetworkRequestProtocol {
associatedtype Resource
var resourceURL: NetworkEndpoint { get set }
var resourceSession: URLSession { get set }
func download() -> AnyPublisher<Resource, NetworkError>
}
有一些自定义类，NetworkEndpoint 和 NetworkError，如果需要，可以在此处添加自己的类，或者使用 URL 和 URLError 代替：
enum NetworkEndpoint {
static let baseURL = URL(string: "API_BASE_URL")! // Add your api base url here
case live
var url: URL {
switch self {
case .live:
return NetworkEndpoint.baseURL!.appendingPathComponent("END_OR_YOUR_API_URL") // Add the end of your API url here
}
}
}
enum NetworkError: LocalizedError {
case addressUnreachable(URL)
case invalidResponse
var errorDescription: String? {
switch self {
case .invalidResponse:
return "The server response is invalid."
case .addressUnreachable(let url):
return "\(url.absoluteString) is unreachable."
}
}
}
现在，我正在创建 NetworkRequest 类来处理 API 调用。 RessourceSession 初始化器仅用于 UnitTest 部分：
final class NetworkRequest<Resource> where Resource: Codable {
var resourceURL: NetworkEndpoint
var resourceSession: URLSession
init(_ resourceURL: NetworkEndpoint,
resourceSession: URLSession = URLSession(configuration: .default)) {
self.resourceURL = resourceURL
self.resourceSession = resourceSession
}
// MARK: - Dispatch Queues
let downloadQueue = DispatchQueue(
label: "downloadQueue", qos: .userInitiated,
attributes: .concurrent, autoreleaseFrequency: .inherit, target: .main)
}
// MARK: - Network Requests
extension NetworkRequest: NetworkRequestProtocol {
func download() -> AnyPublisher<Resource, NetworkError> {
resourceSession
.dataTaskPublisher(for: resourceURL.url)
.receive(on: downloadQueue)
.map(\.data)
.decode(type: Resource.self, decoder: JSONDecoder())
.mapError { error -> NetworkError in
switch error {
case is URLError:
return .addressUnreachable(self.resourceURL.url)
default:
return .invalidResponse }}
.eraseToAnyPublisher()
}
}
对于生产代码，这是一个使用 NetworkRequest 类的例子，当然，你的模型必须是 Codable：
var subscriptions = Set<AnyCancellable>()
func downloadData() {
NetworkRequest<YOUR_MODEL_NAME>(.live).download() // Add your model name inside the brackets
.sink(
receiveCompletion: { completion in
switch completion {
case .failure(let error):
print(error)
case .finished:
break }},
receiveValue: { data in
print(data) })
.store(in: &subscriptions)
}
现在项目中的所有代码都设置好了，我们可以传递给 UnitTest 部分并开始模拟 URLSession：
class MockURLSession: URLSession {
var data: Data?
var response: URLResponse?
var error: Error?
init(data: Data?, response: URLResponse?, error: Error?) {
self.data = data
self.response = response
self.error = error
}
override func dataTask(with request: URLRequest,
completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
let data = self.data
let response = self.response
let error = self.error
return MockURLSessionDataTask {
completionHandler(data, response, error)
}
}
}
现在，我们模拟在 MockURLSession 中覆盖 dataTask 时返回的 URLSessionDataTask，它将适用于 .dataTaskPublisher：
class MockURLSessionDataTask: URLSessionDataTask {
private let closure: () -> Void
init(closure: @escaping () -> Void) {
self.closure = closure
}
override func resume() {
closure()
}
}
我们会创建假响应数据以传递到我们的测试中，但您必须创建一个包含您的数据的 .json 文件才能在测试中获取它们：
class FakeResponseData {
static let response200OK = HTTPURLResponse(url: URL(string: "https://test.com")!,
statusCode: 200,
httpVersion: nil,
headerFields: nil)!
static let responseKO = HTTPURLResponse(url: URL(string: "https://test.com")!,
statusCode: 500,
httpVersion: nil,
headerFields: nil)!
class RessourceError: Error {}
static let error = RessourceError()
static var correctData: Data {
let bundle = Bundle(for: FakeResponseData.self)
let fakeJsonURL = bundle.url(forResource: "FAKE_JSON_FILE_NAME", withExtension: "json") // Add your fake json file name in here
let fakeJsonData = try! Data(contentsOf: fakeJsonURL!)
return fakeJsonData
}
static let incorrectData = "error".data(using: .utf8)!
}
最后，这是您测试 NetworkRequest 的部分，使用来自 .json 文件的虚假数据或错误。您使用 resourceSession 初始化程序在此处添加您的 MockURLSession 并避免进行真正的网络调用：
class NetworkRequestTests: XCTestCase {
var expectation: XCTestExpectation!
var subscriptions: Set<AnyCancellable>!
override func setUpWithError() throws {
try super.setUpWithError()
expectation = XCTestExpectation(description: "wait for queue change")
subscriptions = Set<AnyCancellable>()
}
override func tearDownWithError() throws {
subscriptions = nil
expectation = nil
try super.tearDownWithError()
}
func testNetworkRequest_mockURLSessionAddCorrectDataResponse_returnRatesDataModelValues() throws {
let expectedTestValue = "test" // This value is set in your .json fake data for testing
// This is where you use resourceSession to pass your fake data
let networkRequest = NetworkRequest<RatesData>(.live, resourceSession:
MockURLSession(data: FakeResponseData.correctData,
response: FakeResponseData.response200OK,
error: nil))
networkRequest.download()
.sink(
receiveCompletion: { completion in
self.expectation.fulfill() },
receiveValue: { value in
XCTAssertEqual(expectedTimestamp, value.InFakeJson) // Compare with your fake json file
})
.store(in: &subscriptions)
wait(for: [expectation], timeout: 0.1)
}
func testNetworkRequest_mockURLSessionAddServerErrorAsResponse_returnNetworkErrorInvalidResponse() throws {
let expectedNetworkError = NetworkError.invalidResponse.localizedDescription
// This is where you use resourceSession to pass your fake data
let networkRequest = NetworkRequest<RatesData>(.live, resourceSession:
MockURLSession(data: nil,
response: FakeResponseData.responseKO,
error: nil))
networkRequest.download()
.sink(
receiveCompletion: { completion in
switch completion {
case .failure(let error):
XCTAssertEqual(expectedNetworkError, error.localizedDescription)
case .finished:
break
}
self.expectation.fulfill() },
receiveValue: { value in
XCTAssertNil(value)
})
.store(in: &subscriptions)
wait(for: [expectation], timeout: 0.1)
}
}