How to set Dark Mode in XCUIApplication in swift UITests?

Question

I was wondering if there is a way to set dark mode in-code for the XCUIApplication within a swift UITests project.

I have a need to launch the app in light mode and dark mode in the same test. Setting this in the scheme as a hard coded value will not work, or hacking the simulator from the outside will not work either (for performance & maintainability reasons among others).

Currently I set launch arguments like so:

    let app = XCUIApplication()
    var launchArguments: [AnyHashable] = []
    launchArguments.append("-AppleLanguages")
    launchArguments.append(langCode)
    launchArguments.append("-AppleLocale")
    launchArguments.append(localeCode)
    app.launchArguments = launchArguments
    app.launch()

And it works great.

How do I set Dark Mode for a XCUIApplication instance?

What I've done:

• Extensive search on Apple Development Docs.
• StackOverflow only shows how to hard-code this in the scheme within Xcode, or how to hack the simulator from the outside by killing the simulator, erasing it, and hacking a plist value.

Thanks for any help!

Answer 1

I'm also interested in this question because I'm using UI tests to take screenshots with Fastlane. The goal was to be able to switch between light and dark mode for different tests on the same target.

The solution provided by RobLabs doesn't seem to be working for me on Xcode 11.4 / iOS 13.4. I'm not sure this matches your requirements but I'm using a custom launch argument and then setting the interface style in SceneDelegate, for debug builds only:

In your test:

override func testDarkMode() { // use setUp() to affect all test cases
    app = XCUIApplication()  
    app.launchArguments.append("UITestingDarkModeEnabled")
    app.launch()
}

In SceneDelegate.swift:

func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    (...)

    #if DEBUG
    if CommandLine.arguments.contains("UITestingDarkModeEnabled") {
        window?.overrideUserInterfaceStyle = .dark
    }
    #endif

    (...)    
}

And now your test runs in dark mode.

Answer 2

In macOS, from the Terminal.app, you can issue this command

defaults read NSGlobalDomain AppleInterfaceStyle

Which responds with

Dark

---

In your XCTestCase, this should work

    func testAppleInterfaceStyleDark() {
        let app = XCUIApplication()
        var launchArguments: [AnyHashable] = []

        launchArguments.append("-AppleInterfaceStyle")
        launchArguments.append("Dark")
        app.launchArguments = launchArguments as! [String]
        app.launch()
    }

---

Update as of Xcode 11.4 Beta

You can now toggle the appearance in the Simulator. This is a great way to test maps and other Dark mode features.

• From the Simulator Menu Item > Features > Toggle Appearance, or shift⌘A

Simulator supports toggling appearance for iOS simulators (13.0 and later). From within the app select Debug > Toggle Appearance. From the command line use the simctl ui subcommand, e.g. to set dark appearance

xcrun simctl ui <device> appearance dark