The document discusses the debate around whether or not to write tests for iOS apps. It presents arguments on both sides of the debate, including that tests are not needed, take too much time, and are often broken by new OS releases. It also notes that testing is hard, particularly for UI, but provides tips for better testing practices like writing isolated, fast, and self-verifying tests. The document concludes by offering suggestions for developers who are not writing tests, such as layering code and following principles like YAGNI (You Aren't Gonna Need It).

1. Why we are (not)
writing tests in iOS
apps
by Paul Taykalo, MacPaw
To write or not to write, by Paul Taykalo, #MacPaw 1

2. Plan
To write or not to write, by Paul Taykalo, #MacPaw 2

3. Plan
» Tests vs No "Tests" Fractions
» Tests are not needed
» Need are needed
» I'm trying, but failing
» Aren't we testing already?
» Pivot point
» How not to write tests with success
To write or not to write, by Paul Taykalo, #MacPaw 3

4. Tests
No-Tests
Some-Tests
Groups
To write or not to write, by Paul Taykalo, #MacPaw 4

5. Tests arent't needed
» My grandpa hasn't run a test
» Waste of time
» Just write correct code
» No time
» ???
To write or not to write, by Paul Taykalo, #MacPaw 5

6. To write or not to write, by Paul Taykalo, #MacPaw 6

7. Test all the things
» It's only the right way to do it
» No tests - no feature
To write or not to write, by Paul Taykalo, #MacPaw 7

8. Some-Tests
To write or not to write, by Paul Taykalo, #MacPaw 8

9. Aren't we testing
already?
To write or not to write, by Paul Taykalo, #MacPaw 9

10. Aren't we testing already?
» Debugging
» Logging
» QAs
» End users
To write or not to write, by Paul Taykalo, #MacPaw 10

11. Testing is hard
To write or not to write, by Paul Taykalo, #MacPaw 11

12. Testing is hard
» Big/Small
» Very hard integration
» We don't actually know how
» Boring
» Next time
» Ther's no time atm
To write or not to write, by Paul Taykalo, #MacPaw 12

13. We aren't writing tests. We were
writing tests, but they were too fragile,
and they were breaking for no reason,
so we decided not to
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 13

14. Every time new OS released, all my
snapshot tests are broken. It's not
worth it
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 14

15. Testing is easy
To write or not to write, by Paul Taykalo, #MacPaw 15

16. Testing is easy
» Tests already setup
» Intro/PR/Review
» No commits without Tests ¯_( )_/¯
» It is not fixed unless there's a test
To write or not to write, by Paul Taykalo, #MacPaw 16

17. Why is there so big
difference?
To write or not to write, by Paul Taykalo, #MacPaw 17

18. Starting Test is hard
To write or not to write, by Paul Taykalo, #MacPaw 18

19. To write or not to write, by Paul Taykalo, #MacPaw 19

20. When do we start
thinking about tests?
To write or not to write, by Paul Taykalo, #MacPaw 20

21. Slowing down
To write or not to write, by Paul Taykalo, #MacPaw 21

22. Slowing down
» Not sure everything is fine
» R-word (Regression)
» Fixing bugs time >> Feature time
To write or not to write, by Paul Taykalo, #MacPaw 22

23. Slowing down
» No knowledge
» Huge base
» Different integrations M*N
» Code base/complexity
» Team change
» Same time expectation
To write or not to write, by Paul Taykalo, #MacPaw 23

24. We've slowed down
To write or not to write, by Paul Taykalo, #MacPaw 24

25. What did we
wrong?
To write or not to write, by Paul Taykalo, #MacPaw 25

26. What did we
wrong?
To write or not to write, by Paul Taykalo, #MacPaw 26

27. What did we
wrong?
To write or not to write, by Paul Taykalo, #MacPaw 27

28. What did we
wrong?
To write or not to write, by Paul Taykalo, #MacPaw 28

29. Time to add tests?
To write or not to write, by Paul Taykalo, #MacPaw 29

30. Tests
Expectations vs reality
To write or not to write, by Paul Taykalo, #MacPaw 30

31. Tests
Expectations vs reality
To write or not to write, by Paul Taykalo, #MacPaw 31

32. I added tests they didn't help
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 32

33. Tests are not a cure
Tests are the
insurance
To write or not to write, by Paul Taykalo, #MacPaw 33

34. I spent weeks trying to test UI and
failed all deadlines
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 34

35. Some parts are really
hard to test
Deal with it
To write or not to write, by Paul Taykalo, #MacPaw 35

36. There are a lot of tests, but the code
doesn't seem to be better
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 36

37. Tests won't make your code
significantly better*
To write or not to write, by Paul Taykalo, #MacPaw 37

38. You still can write ugly code
To write or not to write, by Paul Taykalo, #MacPaw 38

39. Your tests can be ugly as well
To write or not to write, by Paul Taykalo, #MacPaw 39

40. The Good, The Bad
and The Ugly
To write or not to write, by Paul Taykalo, #MacPaw 40

41. The Bad
To write or not to write, by Paul Taykalo, #MacPaw 41

42. The Bad
func testImtheS() {
let url = "http://agileinaflash.com/feeds/posts/default"
let content = Data(withContensOfURL:URL(string:url))!
XCTAssertNotNil(content)
let parsedContent = parse(content)!
let rss = RSS(from: parsedContent)!
XCTAssertEqual(rss.title, title)
}
To write or not to write, by Paul Taykalo, #MacPaw 42

43. The Bad
func testImtheS() {
let url = "http://agileinaflash.com/feeds/posts/default"
let content = Data(withContensOfURL:URL(string:url))!
XCTAssertNotNil(content)
let parsedContent = parse(content)!
let rss = RSS(from: parsedContent)!
XCTAssertEqual(rss.title, title)
}
To write or not to write, by Paul Taykalo, #MacPaw 43

44. The Bad
func testImtheS() {
let url = "http://agileinaflash.com/feeds/posts/default"
let content = Data(withContensOfURL:URL(string:url))!
XCTAssertNotNil(content)
let parsedContent = parse(content)!
let rss = RSS(from: parsedContent)!
XCTAssertEqual(rss.title, title)
}
To write or not to write, by Paul Taykalo, #MacPaw 44

45. The Bad
func testImtheS() {
let url = "http://agileinaflash.com/feeds/posts/default"
let content = Data(withContensOfURL:URL(string:url))!
XCTAssertNotNil(content)
let parsedContent = parse(content)!
let rss = RSS(from: parsedContent)!
XCTAssertEqual(rss.title, title)
}
To write or not to write, by Paul Taykalo, #MacPaw 45

46. The Ugly
To write or not to write, by Paul Taykalo, #MacPaw 46

47. The Ugly
func testEncoding() {
let path = "Foo/Bar/Baz"
let info = ["Key": "Hello World"]
let request1 = XPCRequest(path: path, info: info)
let data1 = request1.encode()
let decoded1 = XPCRequest(with: data1)!
XCTAssertEqual(request1.path, decoded1.path)
XCTAssertTrue(NSDictionary(dictionary: request1.info!).isEqual(to: decoded1.info!))
let request2 = XPCRequest(path: path, info: nil)
let data2 = request2.encode()
let decoded2 = XPCRequest(with: data2)!
XCTAssertEqual(request2.path, decoded2.path)
XCTAssertNil(request2.info)
}
To write or not to write, by Paul Taykalo, #MacPaw 47

48. The Ugly
func testMenuItemCreated() throws {
let simulatedClickedRow = 7
let simulatedItems = ["Hello", " World!"]
let mapperExpectation = expectation(description: "mapper should be called")
let mapper: ([Any]) -> [String]? = { objects in
mapperExpectation.fulfill()
return objects as? [String]
}
let formatExpectation = expectation(description: "format should be called")
let format: ([String], Int, Localization.Type) -> String? = { strings, clickedRow, localization in
formatExpectation.fulfill()
XCTAssertEqual(strings, simulatedItems)
XCTAssertEqual(clickedRow, simulatedClickedRow)
return strings.reduce("") { $0 + $1 }
}
let action: ([String], Int) -> Void = { _, _ in }
let keyEquivalent: String = "Key"
let builder = MenuItemBuilder<String>(keyEquivalent: keyEquivalent, mapper: mapper, format: format, action: action)
let menuItem = try require(builder.item(from: simulatedItems, with: simulatedClickedRow))
XCTAssertEqual(menuItem.keyEquivalent, keyEquivalent)
XCTAssertEqual(menuItem.title, "Hello World!")
waitForExpectations(timeout: 0.0) { error in
XCTAssertFalse(error != nil)
}
}
To write or not to write, by Paul Taykalo, #MacPaw 48

49. The Good
To write or not to write, by Paul Taykalo, #MacPaw 49

50. F. I. R. S. T.
To write or not to write, by Paul Taykalo, #MacPaw 50

51. F. I. R. S. T.
» Fast — tests should be able to be executed often.
» Isolated — tests on their own cannot depend on external
factors or on the result of another test.
» Repeatable — tests should have the same result every time we
run them.(*)
» Self-verifying — tests should include assertions; no human
intervention needed.
» Timely — tests should be written along with the production
To write or not to write, by Paul Taykalo, #MacPaw 51

52. The Good
- (void)testAddMalwareInformationCanBeReadFromDataBase {
// Given
TestMalwareInfo info = [self.knowledgeBase _addMalwareInfo];
// When
NSDictionary *malwareInfo = [self.knowledgeBase malwareInfoForItem:nil hash:info.hash];
// Then
XCTAssertEqualObjects(malwareInfo[CMMalwareInfoKeyName], info.name);
XCTAssertEqualObjects(malwareInfo[CMMalwareInfoKeyType], info.type);
}
To write or not to write, by Paul Taykalo, #MacPaw 52

53. The Good
- (void)testMalwareDetectionTasksReturnsMalwareModels {
// Given
MPFileSizerMockWithStubbedAnyPath(^(MPFileSize size) {
CMMalwaresDetectionTask * sut = [self _sutWithItemsCount:3 malwaresCount:2];
// When
CMScanResult *result = [sut scan];
CMEntity *entity = [result.items firstObject];
// Then
XCTAssertTrue([entity isKindOfClass:[CMMalwareModel class]]);
});}
To write or not to write, by Paul Taykalo, #MacPaw 53

54. The Good
- (void)testMalwareDetectionTasksReturnsMalwareModels {
// Given
MPFileSizerMockWithStubbedAnyPath(^(MPFileSize size) {
CMMalwaresDetectionTask * sut = [self _sutWithItemsCount:3 malwaresCount:2];
// When
CMScanResult *result = [sut scan];
CMEntity *entity = [result.items firstObject];
// Then
XCTAssertTrue([entity isKindOfClass:[CMMalwareModel class]]);
});}
To write or not to write, by Paul Taykalo, #MacPaw 54

55. The Good
- (void)testMalwareDetectionTasksReturnsMalwareModels {
// Given
MPFileSizerMockWithStubbedAnyPath(^(MPFileSize size) {
CMMalwaresDetectionTask * sut = [self _sutWithItemsCount:3 malwaresCount:2];
// When
CMScanResult *result = [sut scan];
CMEntity *entity = [result.items firstObject];
// Then
XCTAssertTrue([entity isKindOfClass:[CMMalwareModel class]]);
});}
To write or not to write, by Paul Taykalo, #MacPaw 55

56. The Good
- (void)testMalwareDetectionTasksReturnsMalwareModels {
// Given
MPFileSizerMockWithStubbedAnyPath(^(MPFileSize size) {
CMMalwaresDetectionTask * sut = [self _sutWithItemsCount:3 malwaresCount:2];
// When
CMScanResult *result = [sut scan];
CMEntity *entity = [result.items firstObject];
// Then
XCTAssertTrue([entity isKindOfClass:[CMMalwareModel class]]);
});}
To write or not to write, by Paul Taykalo, #MacPaw 56

57. Why aren't we writing
tests?
To write or not to write, by Paul Taykalo, #MacPaw 57

58. Why aren't we writing tests?
» Too small (project)
» Simple project
» Clear code
» No complaints from product owner/users
To write or not to write, by Paul Taykalo, #MacPaw 58

59. Some tips for
those who
doesn't write
tests
To write or not to write, by Paul Taykalo, #MacPaw 59

60. Some tips for
those who
doesn't write
tests
To write or not to write, by Paul Taykalo, #MacPaw 60

61. Don't show/require all data
YAGNI
struct User {
let id: String
let name: String
let address: String
let friends: [User]
let dogName: String?
let hairStyle: HairStyle
...
}
To write or not to write, by Paul Taykalo, #MacPaw 61

62. Own Data layer
Layer things out
class AppApi {
func getUser(by id: String)
-> SignalProducer<User, AppApiError>
}
To write or not to write, by Paul Taykalo, #MacPaw 62

63. Layer things out
enum AppApiError: Error {
case userNotLoggedIn
case serverFeelsBad
case subscriptionEnded
case unknown(NetworkError) //
}
To write or not to write, by Paul Taykalo, #MacPaw 63

64. Layer things out
// Struct for showing error imeediately to the user
struct UserError {
let title: String
let message: String
// just in some really rare cases
let underlyingError: Error
}
To write or not to write, by Paul Taykalo, #MacPaw 64

65. Don't allow invalid data
struct UserForm {
let id: String?
let name: String?
let lastName: String?
}
struct User {
let id: String
let name: String
let lastName: String
}
To write or not to write, by Paul Taykalo, #MacPaw 65

66. Isolate Order Dependent Code
dataSource.addItems(["1","2","3")
tableView.insertItems(at indexPaths:[IndexPath])
tableView.deleteItems(at indexPaths:[])
tableView.reloadData()
To write or not to write, by Paul Taykalo, #MacPaw 66

67. Semantic meaning
if itemsCount > 4
if user.rating > 200 && user.userName.isNotEmpty
if view.tag == 13
To write or not to write, by Paul Taykalo, #MacPaw 67

68. Unidirectional data
flow
To write or not to write, by Paul Taykalo, #MacPaw 68

69. Linear code
loginUser(onSuccess: { user in
getAllImages(for: user, onSuccess: { images is
verify(images: images, onSuccess: { verified, unverified is
verifyDeletion(images: unverified, onSuccess: { shouldDelete in
},
onFailure: {
// TODO Handle it
print(error)
})
},
onFailure: {
// TODO Handle it
print(error)
})
},
onFailure: {
// TODO Handle it
print(error)
})
},
onFailure: {
// TODO Handle it
print(error)
})
To write or not to write, by Paul Taykalo, #MacPaw 69

70. Linear code
loggeduserRequest
.flatMap(.latest, { user in getAllimages(for: user)})
.flatMap(.latest, { images in verify(images: images)})
.flatMap { verified, unverified in askForDeletion(images: unverified)}
.filter { shouldDelete in deleteImages(shouldDelete) }
To write or not to write, by Paul Taykalo, #MacPaw 70

71. Linear code
loggeduserRequest
.flatMap(.latest, getAllimages)
.flatMap(.latest, verify)
.flatMap { verified, unverified in askForDeletion(images: unverified)}
.filter(deleteImages)
To write or not to write, by Paul Taykalo, #MacPaw 71

72. Non failable code
file.open()
guard something else { file.close(); return}
file.read()
file.close()
To write or not to write, by Paul Taykalo, #MacPaw 72

73. Non failable code
extension File {
func opened(process: (File -> Void)) {
open()
process(self)
close();
}
}
file.opened { f in
guard something else { return }
f.read()
}
To write or not to write, by Paul Taykalo, #MacPaw 73

74. Decrease amount of possible
states
» Optionals
» BFO (Object)
» Exponential number of states
» Mutability
To write or not to write, by Paul Taykalo, #MacPaw 74

75. Some tips for those who doesn't
write tests
» Don't show/require all data
» Layer things out
» Don't allow invalid data
» Semantic meaning
» Linear flow
» Decrease amount of possible states
To write or not to write, by Paul Taykalo, #MacPaw 75

76. More tips for those
who doesn't write
tests
To write or not to write, by Paul Taykalo, #MacPaw 76

77. More tips for those who doesn't
write tests
» Visual snapshots
» Revealing hidden info (i.e. Analytics)
» Logs
To write or not to write, by Paul Taykalo, #MacPaw 77

78. How (not) to fail
adding tests
To write or not to write, by Paul Taykalo, #MacPaw 78

79. How (not) to fail adding tests
» Read a lot about testing and types of testing
» Try to test-first, try to test-last
» Determine your core
» Isolate features and test them
» Start with Unit tests
» For Custom UI you can run snapshot testing
» Hire someone and let them help you
To write or not to write, by Paul Taykalo, #MacPaw 79

80. Te$t$
To write or not to write, by Paul Taykalo, #MacPaw 80

81. - I won't pay additionally for tests
- But there'll be bugs
- They'll be there even if you write tests!
To write or not to write, by Paul Taykalo, #MacPaw 81

82. Tests readiness
To write or not to write, by Paul Taykalo, #MacPaw 82

83. There are many ways to write an
application. We're not building
spaceships, you know?
— Unknown programmer
To write or not to write, by Paul Taykalo, #MacPaw 83

84. Thank you
To write or not to write, by Paul Taykalo, #MacPaw 84

85. Q & A
To write or not to write, by Paul Taykalo, #MacPaw 85

86. Why we are (not)
writing tests in iOS
apps
by Paul Taykalo, MacPaw
@TT_Kilew
To write or not to write, by Paul Taykalo, #MacPaw 86

87. The end
To write or not to write, by Paul Taykalo, #MacPaw 87

88. Bonus
Building a Swift Quiz App with TDD
and Modular Design
https://goo.gl/cUzTkr
To write or not to write, by Paul Taykalo, #MacPaw 88

89. Links
http://merowing.info/2017/01/testing-ios-apps/
https://www.swiftbysundell.com/posts/testing-swift-code-
that-uses-system-singletons-in-3-easy-steps?
utmcontent=buffer1765f&utmmedium=social&utmsource=twitter.co
m&utmcampaign=buffer
https://www.joelonsoftware.com/2001/07/31/hard-assed-bug-
fixin/
https://www.objc.io/issues/15-testing/bad-testing-practices/
To write or not to write, by Paul Taykalo, #MacPaw 89

90. More links
https://medium.com/essential-developer-ios
To write or not to write, by Paul Taykalo, #MacPaw 90