MockSession.swift

class MockSession: URLSession {
    
    var completionHandler: ((Data, URLResponse, Error) -> Void)?
    static var mockResponse: (data: Data?, URLResponse: URLResponse?, error: Error?)

    override class var shared: URLSession {
        return MockSession()
    }
    
    override func dataTask(with request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
        self.completionHandler = completionHandler
        return MockTask(response: MockSession.mockResponse, completionHandler: completionHandler)
    }
    
}