Unit Testing in iOS

I talk about unit testing in iOS and best practices

Transcript

1. Unit Testing in
   iOS
   

   View Slide

2. About
   → Khoa Pham
   → onmyway133.github.io
   

   View Slide

3. View Slide

4. Unit Test
   → What
   → Why
   → How
   → Good Pratices
   

   View Slide

5. F.I.R.S.T.
   → Fast
   → Independent
   → Repeatable
   → Self validating
   → Timely
   

   View Slide

6. What
   Unit test is code that tests a unit of code.
   → Automate
   → Trustworthy
   → Examine all possible cases
   

   View Slide

7. Why
   → Verify
   → Act as documentation
   → Decouple components
   → Avoid regression bugs
   → Refactoring
   

   View Slide

8. Code from others
   

   View Slide

9. Complex operation
   

   View Slide

10. Complex control flow
    

    View Slide

11. Assumption
    

    View Slide

12. Edge cases
    

    View Slide

13. XCTest
    → Unit tests
    → Performance tests
    → UI tests
    

    View Slide

14. Property testing
    property("The reverse of the reverse of an array is that array") <- forAll { (xs : [Int]) in
    return
    (xs.reverse().reverse() == xs) > "Left identity"
    ^&&^
    (xs == xs.reverse().reverse()) > "Right identity"
    }
    

    View Slide

15. Snapshot testing
    class MyViewControllerTests: XCTestCase {
    func testMyViewController() {
    let vc = MyViewController()
    assertSnapshot(matching: vc, as: .image)
    }
    }
    

    View Slide

16. BDD style
    → Behavior driven developmennt
    → RSpec
    describe HelloWorld do
    context “When testing the HelloWorld class” do
    it "should say 'Hello World' when we call the say_hello method" do
    hw = HelloWorld.new
    message = hw.say_hello
    expect(message).to eq "Hello World!"
    end
    end
    end
    

    View Slide

17. BDD in Swift
    context("a move that was already played") {
    it("should throw an error") {
    try! board.play(at: 0) // 1
    // 2
    expect { try board.play(at: 0) }
    .to(throwError(Board.PlayError.alreadyPlayed))
    }
    }
    

    View Slide

18. XCTest
    class HourFormatterTests: XCTestCase {
    func testFormat() {
    let formatter = HourFormatter()
    XCTAssertEqual(formatter.format(minute: 90 ), "01:30")
    XCTAssertEqual(formatter.format(minute: 120), "02:00")
    XCTAssertEqual(formatter.format(minute: 660 ), "11:00")
    }
    }
    

    View Slide

19. TDD
    → Test driven development
    → TDD is dead. Long live testing https://dhh.dk/
    2014/tdd-is-dead-long-live-testing.html
    Less emphasis on unit tests, because we're no
    longer doing test-first as a design practice, and
    more emphasis on, yes, slow, system tests.
    

    View Slide

20. Cons of unit test
    → Take time
    → Code change
    → Take time
    → Compromised test
    → Take time
    

    View Slide

21. Still
    → It's good to have unit test
    → Does not matter if TDD or not. As long as we have
    tests
    → Validate quickly and reliably
    → Help your future self or other maintainers
    

    View Slide

22. Good practices
    

    View Slide

23. 1. Test alongside code
    → Jest https://jestjs.io/
    

    View Slide

24. View Slide

25. 2. Test what you feel need
    import XCTest
    @testable import Cutters_Staging
    class LauncScreenTests: XCTestCase {
    func testLaunchScreen() {
    let launchScreen = UIStoryboard(name: "LaunchScreen", bundle: nil)
    let viewController = launchScreen.instantiateInitialViewController()!
    let label = viewController.view.subviews.compactMap({ $0 as? UILabel }).first!
    XCTAssertEqual(label.text, "Cut time. Cut hair. Cut cost.")
    let imageView = viewController.view.subviews.compactMap({ $0 as? UIImageView }).first!
    XCTAssertNotNil(imageView.image)
    }
    }
    

    View Slide

26. 3. View be dumb
    → Decouple representation (view) from computation
    (logic)
    → Model - View - Controller
    → Test logic
    → And can also test UI
    

    View Slide

27. View Slide

28. 4. Mock
    → Mock during development
    → Mock during testing
    final class Deps {
    static let salonRepo: SalonRepoAware = SalonRepo()
    static let userRepo: UserRepoAware = UserRepo()
    static let cardRepo: CardRepoAware = CardRepo()
    }
    

    View Slide

29. View Slide

30. 5. Commit hook
    → pre-commit
    marker=""
    test $(git diff --cached -z $against | grep $marker | wc -c) != 0
    

    View Slide

31. 6. Coverage
    → Code coverage != Test coverage
    → 100% code coverage
    

    View Slide

32. View Slide

33. 7. Continuous integration
    → Jenkins
    → Bitrise
    → Circle
    → Xcode Server
    

    View Slide

34. View Slide

35. 8. Xcode
    → XCTWaiter Xcode 8.3
    → XCUISiriService in Xcode 9
    → Parallel testing Xcode 10
    → XCTestPlan Xcode 11
    → Simulation, random order, attachment, activity, ...
    

    View Slide

36. View Slide

37. $ xcodebuild test -scheme MyApp \
    -destination "plaform=iOS,name=iPhone 8" \
    -destination "platform=iOS,name=iPhone 8 Plus"
    

    View Slide

38. One more thing
    https://www.youtube.com/watch?v=D-dj_cwdVYg
    

    View Slide

39. Thank you
    M̶a̶y̶ ̶t̶h̶e̶ ̶f ̶o̶r̶c̶e̶ ̶b̶e̶ ̶w̶ i ̶ t̶h̶ ̶y̶o̶u̶
    May your code continue to compile
    

    View Slide