koromiko

class HttpClient {
    typealias completeClosure = ( _ data: Data?, _ error: Error?)->Void
    private let session: URLSession
    init(session: URLSessionProtocol) {
        self.session = session
    }
    func get( url: URL, callback: @escaping completeClosure ) {
        let request = NSMutableURLRequest(url: url)
        request.httpMethod = "GET"
        let task = session.dataTask(with: request) { (data, response, error) in

koromiko

let task = URLSession.shared.dataTask()

koromiko

let task = session.dataTask()

koromiko

class HttpClientTests: XCTestCase { 
    var httpClient: HttpClient! 
    let session = MockURLSession()
    override func setUp() {
        super.setUp()
        httpClient = HttpClient(session: session)
    }
    override func tearDown() {
        super.tearDown()
    }

koromiko

func test_get_request_withURL() {
    guard let url = URL(string: "https://mockurl") else {
        fatalError("URL can't be empty")
    }
    httpClient.get(url: url) { (success, response) in
        // Return data
    }
    // Assert 
}

koromiko

let task = session.dataTask(with: request) { (data, response, error) in
    callback(data, error)
}
task.resume()

koromiko

class MockURLSession {
    private (set) var lastURL: URL?
    func dataTask(with request: NSURLRequest, completionHandler: @escaping DataTaskResult) -> URLSessionDataTask {
        lastURL = request.url
        completionHandler(nextData, successHttpURLResponse(request: request), nextError)        
        return // dataTask, will be impletmented later
    }
}

koromiko

func test_get_request_withURL() {
    guard let url = URL(string: "https://mockurl") else {
        fatalError("URL can't be empty")
    }
    httpClient.get(url: url) { (success, response) in
        // Return data
    }
    XCTAssert(session.lastURL == url)
}

koromiko

class MockURLSessionDataTask {  
    func resume() { }
}

koromiko

class HttpClientTests: XCTestCase {
    var httpClient: HttpClient!
    let session = MockURLSession()
    override func setUp() {
        super.setUp()
        httpClient = HttpClient(session: session) // Doesn't compile 
    }
    override func tearDown() {
        super.tearDown()
    }