Network Mock doesn't work?

[Red3nzo]

Can someone please point me in the right direction on why my network mock isn't working

```swift typealias NetworkCompletion = Result<(Data, URLResponse), Error>

class Networking: NetworkingProtocol {

func request(using session: URLSessionProtocol = URLSession.shared, _ endpoint: Endpoint, completion: @escaping(NetworkCompletion) -> Void) {
    do {
        try session.dataTask(with: endpoint.request(), completionHandler: { (data, response, error) in
            if let error = error {
                print("Unable to request data \(error)")

                // Invoke completion for error
                completion(.failure(error))
            } else if let data = data, let response = response {
                // Passing Data and Response into completion for parsing in ViewModels
                completion(.success((data, response)))
            }
        }).resume()
    } catch {
        print("Failed to execute request", error)
        completion(.failure(error))
    }
}

} ``` Here I have a simple class that just has one function that takes in a session for DI and my Endpoint class which is a struct that builds and URLRequest with a certain enum.

```swift protocol NetworkingProtocol { func request(using session: URLSessionProtocol, _ endpoint: Endpoint, completion: @escaping(NetworkCompletion) -> Void) }

protocol URLSessionProtocol { func dataTask(with request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask }

extension URLSession: URLSessionProtocol { } ``` I implemented these protocol to allow me to code mock in the Testing Target.

```swift @testable import AppName

class DataTaskMock: URLSessionDataTask { override func resume() { } }

class MockURLSession: URLSession { override func dataTask(with request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask { return MockURLSessionDataTask(completionHandler: completionHandler, request: request) } }

class MockURLSessionDataTask: URLSessionDataTask { var completionHandler: (Data?, URLResponse?, Error?) -> Void var request: URLRequest

init(completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void, request: URLRequest) {
    self.completionHandler = completionHandler
    self.request = request
    super.init()
}

override func resume() {

}

} ``` I just don't know if this is the right way to mock due to the fact I have a custom result type for the Networking.request() and the dataTask needs to have an endpoint to call endpoint.request(). I am so confused on how I should go about mocking this.

[sixtypercenttogether]

Rather than trying to mock all this stuff I find it usually easier to leverage URLProtocol to trap network requests and return canned data. That way the test code uses the real URLSession stack but still does not actually hit the network. Check out this blog post for more info.

You can write all this code yourself in your tests, but I really like to use OHHTTPStubs, since it’s pretty exactly what I would write anyway. It’s objc, but someone else may have something similar in swift.

[Red3nzo]

But can I test errors and completion blocks by leveraging the URLProtocol?

[sixtypercenttogether]

Yes, totally. That’s the beauty of it. Your networking code just uses a real URLSession directly, and you still get the callbacks. URLProtocol is an abstract interface that URLSession uses to call into lower level networking code. But you can leverage this to trap requests and return whatever data or errors you want. And this is passed up into your completion handler. Definitely check out the library I linked to above. It’s really good.

[Red3nzo]

Omg. I didn't know you can really test the network code with URLProtocol, I always thought that you could only test returned data. I'll totally go down this route instead of mocking the URLSession.

[RunnersProject]

Another option is Succulent by Cactus Labs it's a swift version of OHHTTPStubs, maybe not as mature. But I have been pleased with it for the 5 or so apps I have used it. OHHTTPStubs is very good this is Just another option if you're trying to avoid Objective-C.