MockTask.swift

class MockTask: URLSessionDataTask {
    
    typealias Response = (data: Data?, URLResponse: URLResponse?, error: Error?)
    var mockResponse: Response
    let completionHandler: ((Data?, URLResponse?, Error?) -> Void)?
    
    init(response: Response, completionHandler: ((Data?, URLResponse?, Error?) -> Void)?) {
        self.mockResponse = response
        self.completionHandler = completionHandler
    }
    
    override func resume() {
        completionHandler!(mockResponse.data, mockResponse.URLResponse, mockResponse.error)
    }
}