Instantiating UIViewController in a test - ios

Question

I'm working in Swift 2, and would like to test functions within my view controller. I've made a dependency injection-like service which looks like this:
extension UIViewController: {
func getDbService() -> IDbService {
let context = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
return DbService(context: context)
}
}
With this, I can set AppDelegate's context as a mocked one for test purposes. However, the problem arises when I try to instantiate a view controller. Here's the code:
class LoginViewController: UIViewController {
var token: String?
override func viewDidLoad() {
super.viewDidLoad()
let dbService = getDbService()
self.token = dbService.getToken()
//....do stuff with token
}
}
I instantiate the test like so:
class LoginViewControllerTests: XCTestCase {
func testTokenExists() {
let mockContext = MockContextUtils.getMockContext()
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.managedObjectContext = mockContext
let sut = LoginViewController()
let _ = sut.view // Apparently this renders the view; I set a breakpoint, viewDidLoad is called
XCTAssertNotNil(sut.token) // FAILS, BECAUSE APPDELEGATE CALLS APP DATABASE, AND NOT MOCK.
}
}
The reason this simple test fails is because LoginViewController has no idea what app delegate is. Is there a way to introduce that in the initialization phase?

Answer 1

So it appears that initializing the view controller with its default controller does not grab the app delegate which we set up in the test. Instead, I've initialized the view controller through the storyboard via so:
let storyboard = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle())
let sut = storyboard.instantiateInitialViewController() as? LoginViewController
XCTAssertNotNil(sut)
XCTAssertNotNil(sut.view)
XCTAssertNotNil(sut.token)
which solves the problem.