3 easy tips for testing your view controller in Swift.

1. everythingyou(n)everwanted
toknowabouttestingview
controllers

2. unittestingisgreat…

3. …foryourmodellayer
- Model layer is easy to test
- Most examples of testing/TDD show model layer tests

4. canyoueventestview
controllers?
- But view controllers—ugh!
- Can you even test them?

5. - Yes!
- This is unfortunate misconception among many iOS devs

6. - Yes!
- This is unfortunate misconception among many iOS devs

7. 1.Appmodule
2.Manuallifecycleevents
3.Storyboardaccessibility
- Just a few simple tricks

8. - We’ll be testing my stealth mode app, BananaApp, made up of one view controller, BananaViewController

9. - We’ll be testing my stealth mode app, BananaApp, made up of one view controller, BananaViewController

10. 1.Appmodule
2.Manuallifecycleevents
3.Storyboardaccessibility
- Public class
- App defines a Swift module

11. - Defines module = YES -> classes in app exported as module
- “Product module name” is the name of what you import in test file

12. // BananaViewController.swift
public class BananaViewController: UIViewController {
// ...
}
- To test classes, they must be exported in module, so they must be public
- This goes for all classes, not just view controllers

13. // BananaViewControllerTests.swift
import BananaApp
import XCTest
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
// ...
}
- We import our defined module
- Since class is public, we can reference it from imported module

14. // BananaViewControllerTests.swift
import BananaApp
import XCTest
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
// ...
}
- We import our defined module
- Since class is public, we can reference it from imported module

15. // BananaViewControllerTests.swift
import BananaApp
import XCTest
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
// ...
}
- We import our defined module
- Since class is public, we can reference it from imported module

16. 1.Appmodule
2.Manuallifecycleevents
3.Storyboardaccessibility
- When app runs, view controller lifecycle methods are triggered automatically.
- In tests, you’ll need to trigger methods like viewDidLoad: yourself.

17. // BananaViewController.swift
import UIKit
public class BananaViewController: UIViewController {
// ...
public override func viewDidLoad() {
super.viewDidLoad()
updateButtons()
}
private func updateButtons() {
moreButton.enabled = bananaCount < 10
lessButton.enabled = bananaCount > 0
}
}
- BananaViewController overrides viewDidLoad to update its buttons
- Let’s test this behavior

18. // BananaViewController.swift
import UIKit
public class BananaViewController: UIViewController {
// ...
public override func viewDidLoad() {
super.viewDidLoad()
updateButtons()
}
private func updateButtons() {
moreButton.enabled = bananaCount < 10
lessButton.enabled = bananaCount > 0
}
}
- BananaViewController overrides viewDidLoad to update its buttons
- Let’s test this behavior

19. // BananaViewController.swift
import UIKit
public class BananaViewController: UIViewController {
// ...
public override func viewDidLoad() {
super.viewDidLoad()
updateButtons()
}
private func updateButtons() {
moreButton.enabled = bananaCount < 10
lessButton.enabled = bananaCount > 0
}
}
- BananaViewController overrides viewDidLoad to update its buttons
- Let’s test this behavior

20. // BananaViewController.swift
import UIKit
public class BananaViewController: UIViewController {
// ...
public override func viewDidLoad() {
super.viewDidLoad()
updateButtons()
}
private func updateButtons() {
moreButton.enabled = bananaCount < 10
lessButton.enabled = bananaCount > 0
}
}
- BananaViewController overrides viewDidLoad to update its buttons
- Let’s test this behavior

21. // BananaViewControllerTests.swift
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
override func setUp() {
viewController = BananaViewController()
let _ = viewController.view
}
func testLessButtonIsDisabled() {
XCTAssertFalse(viewController.lessButton.enabled)
}
}
- Here we test the less button is disabled
- But when we run the tests, they fail
- Need to access view to trigger viewDidLoad

22. // BananaViewControllerTests.swift
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
override func setUp() {
viewController = BananaViewController()
let _ = viewController.view
}
func testLessButtonIsDisabled() {
XCTAssertFalse(viewController.lessButton.enabled)
}
}
- Here we test the less button is disabled
- But when we run the tests, they fail
- Need to access view to trigger viewDidLoad

23. // BananaViewControllerTests.swift
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
override func setUp() {
viewController = BananaViewController()
let _ = viewController.view
}
func testLessButtonIsDisabled() {
XCTAssertFalse(viewController.lessButton.enabled)
}
}
- Here we test the less button is disabled
- But when we run the tests, they fail
- Need to access view to trigger viewDidLoad

24. // BananaViewControllerTests.swift
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
override func setUp() {
viewController = BananaViewController()
let _ = viewController.view
}
func testLessButtonIsDisabled() {
XCTAssertFalse(viewController.lessButton.enabled)
}
}
XCTAssertFalse failed
- Here we test the less button is disabled
- But when we run the tests, they fail
- Need to access view to trigger viewDidLoad

25. // BananaViewControllerTests.swift
class BananaViewControllerTests: XCTestCase {
var viewController: BananaViewController!
override func setUp() {
viewController = BananaViewController()
let _ = viewController.view
}
func testLessButtonIsDisabled() {
XCTAssertFalse(viewController.lessButton.enabled)
}
}
- Here we test the less button is disabled
- But when we run the tests, they fail
- Need to access view to trigger viewDidLoad

26. 1.Appmodule
2.Manuallifecycleevents
3.Storyboardaccessibility
- If your view controller’s interface is buried within a storyboard file, you’ll need to provide a way to access it

27. - You’ll need to give your view controller an ID

28. // BananaViewControllerTests.swift
let storyboard = UIStoryboard(name: "Main", bundle: nil)
viewController =
storyboard.instantiateViewControllerWithIdentifier(
"BananaViewControllerID") as BananaViewController
- You can instantiate any view controller with an ID in your tests
- If it’s the initial view controller in your storyboard, you don’t need an identifier

29. // BananaViewControllerTests.swift
let storyboard = UIStoryboard(name: "Main", bundle: nil)
viewController =
storyboard.instantiateViewControllerWithIdentifier(
"BananaViewControllerID") as BananaViewController
viewController =
storyboard.instantiateInitialViewController()
as BananaViewController
- You can instantiate any view controller with an ID in your tests
- If it’s the initial view controller in your storyboard, you don’t need an identifier

30. public class BananaViewController: UIViewController {
@IBOutlet public weak var countLabel: UILabel!
@IBOutlet public weak var moreButton: UIButton!
@IBOutlet public weak var lessButton: UIButton!
// ...
}
- And remember, XIB and storyboard files set IBOutlet properties during -viewDidLoad

31. // BananaViewControllerTests.swift
let storyboard = UIStoryboard(name: "Main", bundle: nil)
viewController =
storyboard.instantiateViewControllerWithIdentifier(
"BananaViewControllerID") as BananaViewController
let _ = viewController.view
XCTAssertFalse(viewController.lessButton.enabled)
- So if you access an IBOutlet prior to triggering -viewDidLoad, you’ll hit an assert

32. Thread 1: EXC_BAD_INSTRUCTION
// BananaViewControllerTests.swift
let storyboard = UIStoryboard(name: "Main", bundle: nil)
viewController =
storyboard.instantiateViewControllerWithIdentifier(
"BananaViewControllerID") as BananaViewController
let _ = viewController.view
XCTAssertFalse(viewController.lessButton.enabled)
- So if you access an IBOutlet prior to triggering -viewDidLoad, you’ll hit an assert

33. // BananaViewControllerTests.swift
let storyboard = UIStoryboard(name: "Main", bundle: nil)
viewController =
storyboard.instantiateViewControllerWithIdentifier(
"BananaViewControllerID") as BananaViewController
let _ = viewController.view
XCTAssertFalse(viewController.lessButton.enabled)
- So if you access an IBOutlet prior to triggering -viewDidLoad, you’ll hit an assert

34. 1.Appmodule
2.Manuallifecycleevents
3.Storyboardaccessibility
- So remember

35. func testLessButtonAfterAddingBananaIsEnabled() {
viewController.moreButton.sendActionsForControlEvents(
UIControlEvents.TouchUpInside)
XCTAssert(viewController.lessButton.enabled)
}
- With these in mind, we can write tests like this
- Tap the button to add banana, then less button (to remove banana) is enabled

36. func testLessButtonAfterAddingBananaIsEnabled() {
viewController.moreButton.sendActionsForControlEvents(
UIControlEvents.TouchUpInside)
XCTAssert(viewController.lessButton.enabled)
}
- With these in mind, we can write tests like this
- Tap the button to add banana, then less button (to remove banana) is enabled

37. func testLessButtonAfterAddingBananaIsEnabled() {
viewController.moreButton.sendActionsForControlEvents(
UIControlEvents.TouchUpInside)
XCTAssert(viewController.lessButton.enabled)
}
- With these in mind, we can write tests like this
- Tap the button to add banana, then less button (to remove banana) is enabled

40. - But in the end, it’s not as easy as testing regular objects
- So push as much logic into model layer as possible

41. - But in the end, it’s not as easy as testing regular objects
- So push as much logic into model layer as possible

42. thinviewcontrollers!
- Remember, thin view controllers!