Unit Testing in iOS

About → Khoa Pham → onmyway133.github.io

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Unit Test → What → Why → How → Good Pratices

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

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

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

Code from others

Complex operation

Complex control flow

Assumption

Edge cases

XCTest → Unit tests → Performance tests → UI tests

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" }

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

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

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)) } }

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") } }

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.

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

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

Good practices

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

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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) } }

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

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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() }

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

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

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

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

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

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

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