Swift: Testing a URLSession called with delegates - swift

Question

I'm trying to do the unit tests for my app.
I've this function preparing the request
func getWeatherDataAtLocation() {
let WEATHER_URL = "http://api.openweathermap.org/data/2.5/weather"
let weatherAPI = valueForAPIKey(named:"weatherAPI")
let lat = String(locationService.latitude)
let lon = String(locationService.longitude)
do {
try networkService.networking(url: "\(WEATHER_URL)?APPID=\(weatherAPI)&lon=\(lon)&lat=\(lat)", requestType: "weather")
} catch let error {
print(error)
}
}
I've a service class networkservice processing the network request :
class NetworkService {
var weatherDataDelegate: WeatherData?
var session: URLSession
init(session: URLSession = URLSession(configuration: .default)) {
self.session = session
}
func networking(url: String, requestType: String) {
var request = URLRequest(url: requestUrl)
request.httpMethod = "GET"
var task: URLSessionDataTask
task = session.dataTask(with: request) { (data, response, error) in
switch requestType {
case "weather":
do {
let weatherJSON = try JSONDecoder().decode(WeatherJSON.self, from: data)
self.weatherDataDelegate?.receiveWeatherData(weatherJSON)
} catch let jsonErr {
print(jsonErr)
}
case // Other cases
default:
print("error")
}
}
task.resume()
}
}
Then i've the delegate running this function to update the JSON received
func receiveWeatherData(_ data: WeatherJSON) {
self.dataWeather = data
do {
try updateWeatherDataOnScreen()
} catch let error {
print(error)
}
}
The issue is I've no idea how I can write some code to test this and all the ressources I find is to test with a callback, any idea?

Answer 1

So there are mutliple steps in this.
1: Create a mocked version of the response of exactly this request. And save it in a json file. Named like weather.json
2: Once you have done that you want to add an #ifdef testSchemeName when executing request. And tell it to tell your function called networking() to read from a file named "\(requestType).json" instead of making the request.
Optional, more advanced way:
This actually intercepts your request and send you the file data instead. A bit more advanced, but your testing gets 1 level deeper.