Tips and Tricks for Writing Reliable Tests Mani Ramezan @maniramezan 

About me • My name is Mani, written Mani, pronounced Maani • Tech editor in raywenderlich • Software engineer at Comixology • Former employee of Zocdoc 

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Agenda • Types of testing • Challenges with writing reliable tests • Some tips and tricks • Resources 

What kind of tests do you usually include in your apps? • https://www.menti.com/tba5bsjyx3 • Go to www.menti.com and use the code 26 94 7 

Importance level Pyramid of Testing 

Integration vs. UI Test • Integration Test: Aims to test integration between different parts and units of the app • Usually done against mock data • UI Test: Mainly refers to as functional testing, aims to test product integration with other services • Usually done against production code 

Challenges • Tightly coupled with app architecture • Test interactions with server • UI Automation tests tends to be flaky • Local ≠ CI environment 

Challenges cont. • Running all tests could take a long time • Managers tend to check for code coverage vs. test coverage • Rely on backend for ability to test in production 

Tips and Tricks 

Enable Randomize Testing 

Separate AppDelegate • Useful for unit tests • Skip unnecessary setups • Customize data store and services • More details: https://marcosantadev.com/fake- appdelegate-unit-testing-swift/
 let isRunningTests = NSClassFromString("XCTestCase") != nil let appDelegateClass = isRunningTests ? NSStringFromClass(TestAppDelegate.self) : NSStringFromClass(AppDelegate.self) UIApplicationMain(CommandLine.argc, CommandLine.unsafeArgv, nil, appDelegateClass) 

Data Store • Mainly a big issue for unit tests • Need a way to reset data after each unit test • Use in-memory persistent for core data • Be aware of NSUserDefaults 

Network Stubbing • Use a third party library to mock API responses • OHHTTPStub • Useful for unit test and integration tests • Would need alternatives for production testing 

Question What is something that you have found challenging when writing unit tests? 

Environment Variables • Can be used to customize tests • Test universal links and deeplinks • Feature flags • Camera testing 

Reset Warnings and Content • Reset location & Privacy • “Reset Warning” on simulator and “Reset Settings” on device • Run before each UITest test case • resetAuthorizationStatus added in Xcode 11.4 • Access Settings app let settings = XCUIApplication(bundleIdentifier: "com.apple.Preferences") 

Delete the App • Helps with resetting NSUserDefaults • How? https://stackoverflow.com/a/36168101/1450348 • Pros • Clear state • Cons • Increases test runs • Adds to test flakiness 

You Can’t Trust a Machine Was asked to type “aetna dc ppo” but it ended up with “aaetna dc ppo” facepalm 

Always Check Visibility 

Keyboard Interaction • Button title: • ”Search” • “Send” • “Route" • “Join" • “Go" • "Emergency call” • “Done" • “Continue" 

More Tips • Review crash logs • Increase wait interval • Always rely on CI results • Constantly monitoring • Re-visiting app architecture • Write tests for new bugs • Code coverage ≠ quality 

Resources • iOS Unit Testing and UI Testing Tutorial • What's New in Testing (WWDC 2018) • Testing in Xcode • John Sundell • Getting started with Xcode UI testing in Swift • Reduce Flakiness in Swift test • UIKonf 2018 - The Magic of UI Testing • Earlgrey 

Final question What's one tool or exercise that has helped you to develop a better unit test? 

Questions? Mani Ramezan [email protected] @maniramezan