This is a talk from an iOS meeting in Osijek, Croatia. The talk is about the whys and hows of unit testing iOS apps.

1. Unit Testing

2. Zašto?

3. Kako ubiti
2 aplikacije
Jednim commitom.

4. Manje bugova.

5. Swift
migracija?
Nema problema.

6. Manje stresa.

7. Kad se isplati?

8. Testiranje je
investicija

9. Što testirati?
Koliko se koristi?
Koliko je kompleksno?
Koliko je važna korektnost?

10. Što testirati?
1. Core logika
2. Prezentacija (ViewModel)
3. UI

11. Zašto ljudi ne
testiraju?

12. Testovi su
teški.
Ako je dizajn loš.

13. Teško za
testirati:
Dependency (UIKit,
Foundation, libovi)

14. Lagano za
testirati:
“Čisti” Swift
Business logika

15. Granice
Razdvojiti Swift od plaforme i
libraryja
Izdvojiti logiku aplikacije

16. MVVM

17. UIViewController
NAVIGACIJA
UIKIT
PRIKAZ
UI LOGIKA
NETWORKING
BUSINESS
LOGIKA
TRANSFORMA
CIJA
PODATAKA
MIJENJANJE
STANJA

18. UIViewController
NAVIGACIJA
UIKIT
PRIKAZ
UI LOGIKA
NETWORKINGBUSINESS
LOGIKA
TRANSFORMA
CIJA
PODATAKA
MIJENJANJE
STANJA
ViewModel

19. MVVM++

20. Example

21. States
LoadedLoading No data Error

22. States
class FeedViewModel {
enum ViewState {
case loading
case noData
case error(String)
case loaded([FeedCellModel])
}
}

23. Data
struct FeedCellModel {
let name: String
let description: String
let image: URL?
}
Lagano za verificirati,
bez stanja (nepromjenljivo)

24. class FeedViewModel {
func loadData() {
self.state = .loading
feedService.getFeedItem(page: 0) { result in
switch result {
case let .success(items):
if items.isEmpty {
self.state = .noData
} else {
let models = self.feedCellModels(from: items)
self.state = .loaded(models)
}
case let .failure(error):
let errorText = self.errorText(for: error)
self.state = .error(errorText)
}
}
}
}

25. class FeedViewModel {
func loadData() {
self.state = .loading
feedService.getFeedItem(page: 0) { result in
switch result {
case let .success(items):
if items.isEmpty {
self.state = .noData
} else {
let models = self.feedCellModels(from: items)
self.state = .loaded(models)
}
case let .failure(error):
let errorText = self.errorText(for: error)
self.state = .error(errorText)
}
}
}
}

26. class FeedViewModel {
func loadData() {
self.state = .loading
feedService.getFeedItem(page: 0) { result in
switch result {
case let .success(items):
if items.isEmpty {
self.state = .noData
} else {
let models = self.feedCellModels(from: items)
self.state = .loaded(models)
}
case let .failure(error):
let errorText = self.errorText(for: error)
self.state = .error(errorText)
}
}
}
}

27. class FeedViewModel {
func loadData() {
self.state = .loading
feedService.getFeedItem(page: 0) { result in
switch result {
case let .success(items):
if items.isEmpty {
self.state = .noData
} else {
let models = self.feedCellModels(from: items)
self.state = .loaded(models)
}
case let .failure(error):
let errorText = self.errorText(for: error)
self.state = .error(errorText)
}
}
}
}

28. class FeedViewModel {
func loadData() {
self.state = .loading
feedService.getFeedItem(page: 0) { result in
switch result {
case let .success(items):
if items.isEmpty {
self.state = .noData
} else {
let models = self.feedCellModels(from: items)
self.state = .loaded(models)
}
case let .failure(error):
let errorText = self.errorText(for: error)
self.state = .error(errorText)
}
}
}
}

29. class FeedViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
viewModel.onStateChanged = { [weak self] state in
guard let `self` = self else { return }
switch state {
case .noData:
self.refreshControl.endRefreshing()
self.manager.data = []
self.errorImage.isHidden = true
self.errorLabel.text = Localizable.error_empty_feed
self.errorView.isHidden = false
case .error(let error):
self.manager.data = []
self.refreshControl.endRefreshing()
self.errorImage.isHidden = false
self.errorLabel.text = error
self.errorView.isHidden = false
case .loaded(let items):
self.refreshControl.endRefreshing()
self.manager.data = items
self.errorView.isHidden = true
case .loading:
self.refreshControl.beginRefreshing()
}
}
}

30. Prednosti
1. Cijeli state na jednom mjestu
2. Manipulacija statea izdvojena iz iOS-a
3. Lagano ubacivanje dodatnog
statea

31. Prednosti
Testabilan dizajn = dobar dizajn

32. Testiranje
1. Spremi promjenu statea u array.
2. Okini akcije.
3. Provjeri state array.

33. class FeedDetailsViewModelTests: XCTestCase {
var feedService: FeedServiceMock!
var states: [FeedDetailsViewModel.ViewState] = []
var viewModel: FeedDetailsViewModel!
override func setUp() {
super.setUp()
feedService = FeedServiceMock()
states = []
viewModel = FeedViewModel(feedService)
viewModel.onState = { self.states.append($0) }
}

34. class FeedDetailsViewModelTests: XCTestCase {
var feedService: FeedServiceMock!
var states: [FeedDetailsViewModel.ViewState] = []
var viewModel: FeedDetailsViewModel!
override func setUp() {
super.setUp()
feedService = FeedServiceMock()
states = []
viewModel = FeedViewModel(feedService)
viewModel.onState = { self.states.append($0) }
}

35. class FeedDetailsViewModelTests: XCTestCase {
var feedService: FeedServiceMock!
var states: [FeedDetailsViewModel.ViewState] = []
var viewModel: FeedDetailsViewModel!
override func setUp() {
super.setUp()
feedService = FeedServiceMock()
states = []
viewModel = FeedViewModel(feedService)
viewModel.onState = { self.states.append($0) }
}

36. class FeedDetailsViewModelTests: XCTestCase {
var feedService: FeedServiceMock!
var states: [FeedDetailsViewModel.ViewState] = []
var viewModel: FeedDetailsViewModel!
override func setUp() {
super.setUp()
feedService = FeedServiceMock()
states = []
viewModel = FeedViewModel(feedService)
viewModel.onState = { self.states.append($0) }
}

37. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testLoadDataTransitionsToLoadedState() {
viewModel.loadData()
switch (states.first!, states.last!) {
case (.loading, .loaded):
break
default:
XCTFail()
}
}
}

38. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testLoadDataTransitionsToLoadedState() {
viewModel.loadData()
switch (states.first!, states.last!) {
case (.loading, .loaded):
break
default:
XCTFail()
}
}
}

39. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testLoadDataTransitionsToLoadedState() {
viewModel.loadData()
switch (states.first!, states.last!) {
case (.loading, .loaded):
break
default:
XCTFail()
}
}
}

40. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testLoadDataTransitionsToLoadedState() {
viewModel.loadData()
switch (states.first!, states.last!) {
case (.loading, .loaded):
break
default:
XCTFail()
}
}
}

41. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testFeedItemData() {
viewModel.loadData()
switch states.last! {
case .loaded(let data):
XCTAssertEqual(data, self.feedService.mockFeedItems)
default:
XCTFail("Expected `loaded`")
}
}
}

42. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testFeedItemData() {
viewModel.loadData()
switch states.last! {
case .loaded(let data):
XCTAssertEqual(data, self.feedService.mockFeedItems)
default:
XCTFail("Expected `loaded`")
}
}
}

43. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testFeedItemData() {
viewModel.loadData()
switch states.last! {
case .loaded(let data):
XCTAssertEqual(data, self.feedService.mockFeedItems)
default:
XCTFail("Expected `loaded`")
}
}
}

44. final class FeedDetailsViewModelTests: XCTestCase {
// …
func testFeedItemData() {
viewModel.loadData()
switch states.last! {
case .loaded(let data):
XCTAssertEqual(data, self.feedService.mockFeedItems)
default:
XCTFail("Expected `loaded`")
}
}
}

45. Rinse and
repeat.

46. Dependencyji

47. Stub / mock
Preuzeti kontrolu nad
dependencyjem
Lakše testiranje

48. 1.
Dependency
Injection

49. class PersistenceService {
var token: String? {
let defaults = UserDefaults.standard
return defaults.object(forKey: "user_token") as? String
}
}

50. class PersistenceService {
var token: String? {
let defaults = UserDefaults.standard
return defaults.object(forKey: "user_token") as? String
}
}
Implicitni dependency

51. class PersistenceService {
private let defaults: UserDefaults
init(_ defaults: UserDefaults) {
self.defaults = defaults
}
var token: String? {
return defaults.object(forKey: "user_token") as? String
}
}

52. Pozivatelj
kreira
dependency

53. 2.
Dependency
Inversion

54. class PersistenceService {
private let defaults: UserDefaults
init(_ defaults: UserDefaults) {
self.defaults = defaults
}
var token: String? {
return defaults.object(forKey: "user_token") as? String
}
}

55. protocol ObjectStore {
func set(value: Any?, forKey: String)
func object(forKey: String)-> Any?
}

56. protocol ObjectStore {
func set(value: Any?, forKey: String)
func object(forKey: String)-> Any?
}
extension UserDefaults: ObjectStore {}

57. class PersistenceService {
private let defaults: ObjectStore
init(_ defaults: ObjectStore) {
self.defaults = defaults
}
var token: String? {
return defaults.object(forKey: "user_token") as? String
}
}

58. class UserDefaultsMock: ObjectStore {
func object(forKey: String) -> Any? {
}
func set(value: Any?, forKey: String) {
}
}
let userDefaultsMock = UserDefaultsMock()
let persistenceService = PersistenceService(userDefaultsMock)

59. class UserDefaultsMock: ObjectStore {
var data: [String: Any?] = [:]
func object(forKey key: String) -> Any? {
return data[key] ?? nil
}
func set(value: Any?, forKey key: String) {
data[key] = value
}
}

60. final class PersistenceServiceTests: XCTestCase {
var store: ObjectStoreMock!
var service: PersistenceService!
override func setUp() {
super.setUp()
store = ObjectStoreMock()
service = PersistenceService(store)
}
func testRetrievesSavedTokenFromStore() {
store.data["token"] = "savedToken"
XCTAssertEqual(service.token, "savedToken")
}
}

61. Pisanje
mockova.

62. class LoginServiceMock: LoginServiceProtocol {
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
}
}

63. class LoginServiceMock: LoginServiceProtocol {
var loginParameters: (username: String, password: String)?
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
loginParameters = (username, password)
}
}

64. class LoginServiceMock: LoginServiceProtocol {
var loginParameters: (username: String, password: String)?
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
loginParameters = (username, password)
}
}

65. class LoginServiceMock: LoginServiceProtocol {
var loginParameters: (username: String, password: String)?
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
loginParameters = (username, password)
}
}
func testCallsLoginServiceWithCorrectParams() {
loginViewModel.login(
email: "email@mail.com",
password: "123pass")
let expectedParams = ("email@mail.com", "123pass")
XCTAssertEqual(expectedParams,
loginServiceMock.loginParameters)
}

66. var loginShouldSucceed = true
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
if loginShouldSucceed {
completion(.success(UserToken(token: "abc123")))
} else {
completion(.failure(.noInternet))
}
}

67. var loginShouldSucceed = true
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
if loginShouldSucceed {
completion(.success(UserToken(token: "abc123")))
} else {
completion(.failure(.noInternet))
}
}

68. var loginShouldSucceed = true
func login(username: String, password: String,
completion: @escaping (LoginResult)-> Void) {
if loginShouldSucceed {
completion(.success(UserToken(token: "abc123")))
} else {
completion(.failure(.noInternet))
}
}
func testHandlesErrorCorrectly() {
loginServiceMock.loginShouldSucceed = false
loginViewModel.login(email: "mail@mail.com",
password: "123pass")
XCTAssertNotNil(viewModel.errorText)
}

69. Sourcery je
prijatelj.
Link na kraju preze.

70. Pisanje testova

71. Testovi su
teški.

72. Dobri testovi
su teški.

73. Ne prolazi za ni jednu netočnu
implementaciju.
1. Pokrivenost

74. func testHandlesErrorCorrectly() {
loginServiceMock.loginShouldSucceed = false
loginViewModel.login(email: "mail@mail.com",
password: "123pass")
XCTAssertNotNil(viewModel.errorText)
}
Prazan string?

75. Test prolazi za sve korektne
implementacije.
1. Lakoća
refaktoringa

76. func testStoresUsernameCorrectly() {
let store = UserDataStore()
store.store(username: "Marin")
XCTAssertEqual(store.storage["username"], "Marin")
}

77. func testStoresUsernameCorrectly() {
let store = UserDataStore()
store.store(username: "Marin")
XCTAssertEqual(store.storage["username"], "Marin")
}
func testStoresUsernameCorrectly() {
let store = UserDataStore()
store.store(username: "Marin")
XCTAssertEqual(store.storedUsername, "Marin")
}
vs

78. Korektno
+
Fleksibilno

79. Tips & tricks

80. Odaberi dobar
framework

81. Nek te CI
natjera

82. Piši helpere

83. Testiraj nešto

84. Whew!

85. Testing For People Who Hate Testing
https://eev.ee/blog/2016/08/22/testing-for-people-who-hate-testing/
AutoMockable Sourcery template
https://cdn.rawgit.com/krzysztofzablocki/Sourcery/master/docs/mocks.html
Unit Testing in Swift
https://medium.cobeisfresh.com/unit-testing-in-swift-part-1-the-philosophy-9bc85ed5001b