Unit Testing HTTP traffic in Alamofire app

I’m adding another answer since I’ve just found this approach that in my opinion is easier and really simple to read and use.

I’ve created a dummy Alamofire class that contains only the functions and the types necessary for tests.
Now I include this file in the test target instead of the real Alamofire.

For example I’ve created my version of the Request class where I define a couple of static variables that I valorise depending on the test, and for this class I’ve implemented only the init and the responseJSON function.

public class Request {

    var request:String?
    struct response{
        static var data:NSHTTPURLResponse?
        static var json:AnyObject?
        static var error:NSError?
    }

    init (request:String){
        self.request = request
    }

    public func responseJSON(options: NSJSONReadingOptions = .AllowFragments, completionHandler: (NSURLRequest, NSHTTPURLResponse?, AnyObject?, NSError?) -> Void) -> Self {

        completionHandler(NSURLRequest(URL: NSURL(string:self.request!)!), Request.response.data, Request.response.json, Request.response.error)
        return self
    }
}

Now I can mock a response in a test:

func testMytestFunction(){
    var HTMLResponse = NSHTTPURLResponse(URL: NSURL(string: "myurl")!, statusCode: 200, HTTPVersion: "HTTP/1.1", headerFields: nil)

    Request.response.data = HTMLResponse
    Request.response.json = LoadDataFromJSONFile("MyJsonFile")

    request(.POST, "myurl", parameters: nil, encoding: ParameterEncoding.JSON).responseJSON {
        (request, response, JSON, error) -> Void in
        // the JSON and response variable now contains exactly the data that you have passed to Request.response.data and Request.response.json
    }
}

The request function is defined here:

public func request(method: Method, URLString: URLStringConvertible, parameters: [String: AnyObject]? = nil, encoding: ParameterEncoding = .URL) -> Request {

    return Request(request: URLString.URLString)
}

public func request(URLRequest: URLRequestConvertible) -> Request {

    return Request(request: "fakecall")
}