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Handle interruptions and alerts in UI tests

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Learn how to anticipate potential interruptions to your app’s interface and build smart tests to identify them. UI interruptions often appear indeterminately, typically during onboarding or first launch, which can make them hard to track down. Learn how to understand interruptions, write stronger tests with UI interruption handlers, and manage expected alerts. To learn more about the latest improvements for testing your app in Xcode, check out “XCTSkip your tests”, “Get your test results faster”, and “Triage test failures with XCTIssue”.

What an UI interruption?

An element that:

  • appears unexpectedly
  • blocks access to another element (which an UI test is trying to interact with)

Common interruptions:

  • banner notifications
  • alerts/dialogs

What are UI interruptions handlers?

  • closures
  • XCTest maintains a stack of handlers
  • XCTest uses LIFO: the last handler registered is the first to be invoked
  • the stack resets between tests

If an interruption handler successfully handled an interruption, it returns true and the UI test continues. If it was not able to handle the interruption, it returns false and the next handler is invoked.

iOS has built-in interruption handlers for alerts: - taps cancel button if any, falls back to the default button otherwise

(New in Xcode 12) iOS has built-in interruption handlers for banners: - swipe to dismiss persistent banners - wait for temporary banners to auto-dismiss

macOS has built-in interruption handlers for:

  • permission dialogs: chooses Don't Allow
  • Bluetooth Setup Assistant: closes window

When UI interruptions handlers are not triggered

Not all alerts will trigger UI interruptions handlers:

How to interact with expected alerts

Use addUIInterruptionMonitor(withDescription:handler:) to add a new interruption monitor. The system will automatically invoke the interruption handler stack when the UI test tries to interact with something that is blocked by an interruption.

The following example tries to tap the Retry button on an alert (if interrupted by it):

addUIInterruptionMonitor(withDescription: "Handle recipe update failures") { element -> Bool in
    let retryButton = element.buttons["Retry"].firstMatch
    if element.elementType == .alert && retryButton.exists {
        retryButton.tap()
        return true
    } else {
        return false
    }
}

Protected resources

From Xcode 11.4, iOS and tvOS 13.4, and macOS 10.15.4, we have a new resetAuthorizationStatus(for:) API to reset the authorization status for a protected resource (it will be like it was never asked before).

Note that the app will be killed when this api is called, therefore a way to use this API is the following:

func testAddingPhotosFirstTime() throws {
    let app = XCUIApplication()
    app.resetAuthorizationStatus(for: .photos)

    app.launch()

    // Test code…
}

Missing anything? Corrections? Contributions are welcome 😃

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Written by

zntfdr

Federico Zanetello

Federico Zanetello is an iOS Engineer with strong passion for Swift, minimalism, and design. When he’s not busy automating things, he can be found writing at fivestars.blog and/or playing with the latest shiny toys.