S01E06: [TDD 🍅 5] Testing View Controllers in Swift

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It’s time to start the UI

First, create a new Project called QuizApp using Storyboards and Swift. Don’t fret 😮‍💨, we’ll look at using SwiftUI in future sessions!

Next, follow these steps:

1. Delete the ViewController.swift, Main.storyboard, and SceneDelegate.swift
2. Add var window: UIWindow? to AppDelegate.swift
3. Remove UISceneSession Lifecycle ( functions ) in AppDelegate
4. In target QuizApp > Info remove Main storyboard file base name
5. Update your Info.plist file to the following:

Our AppDelegate will look like this:

import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        return true
    }
}

Now, build and run (⌘R) and you should have an application that compiles and launches a simulator with a black screen. 🎉

Start with a test!

Create a QuestionViewControllerTests.swift file under the unit test target.

import XCTest

class QuestionViewControllerTests: XCTestCase {}

We’ll start by writing a test to verify the correct question text is displayed as a header.

func test_viewDidLoad_rendersQuestionHeaderText() {
    XCTAssertEqual(sut.headerLabel.text, "Q1")
}

In order to test ViewControllers we need first to invoke their view lifecycle so that they are in a ready state. This is the same process when displaying our UI on the device.

func test_viewDidLoad_rendersQuestionHeaderText() {
        
    _ = sut.viewDidLoad // ❌ Don't do this!
    
    XCTAssertEqual(sut.headerLabel.text, "Q1")
}