axiom-ui-testing（公理 UI 测试）

UI Testing

Overview

Wait for conditions, not arbitrary timeouts. Core principle Flaky tests come from guessing how long operations take. Condition-based waiting eliminates race conditions.

NEW in WWDC 2025: Recording UI Automation allows you to record interactions, replay across devices/languages, and review video recordings of test runs.

Example Prompts

These are real questions developers ask that this skill is designed to answer:

1. "My UI tests pass locally on my Mac but fail in CI. How do I make them more reliable?"

→ The skill shows condition-based waiting patterns that work across devices/speeds, eliminating CI timing differences

2. "My tests use sleep(2) and sleep(5) but they're still flaky. How do I replace arbitrary timeouts with real conditions?"

→ The skill demonstrates waitForExistence, XCTestExpectation, and polling patterns for data loads, network requests, and animations

3. "I just recorded a test using Xcode 26's Recording UI Automation. How do I review the video and debug failures?"

→ The skill covers Video Debugging workflows to analyze recordings and find the exact step where tests fail

4. "My test is failing on iPad but passing on iPhone. How do I write tests that work across all device sizes?"

→ The skill explains multi-factor testing strategies and device-independent predicates for robust cross-device testing

5. "I want to write tests that are not flaky. What are the critical patterns I need to know?"

→ The skill provides condition-based waiting templates, accessibility-first patterns, and the decision tree for reliable test architecture

Red Flags — Test Reliability Issues

If you see ANY of these, suspect timing issues:

• Tests pass locally, fail in CI (timing differences)
• Tests sometimes pass, sometimes fail (race conditions)
• Tests use sleep() or Thread.sleep() (arbitrary delays)
• Tests fail with "UI element not found" then pass on retry
• Long test runs (waiting for worst-case scenarios)

Quick Decision Tree

Test failing?
├─ Element not found?
│  └─ Use waitForExistence(timeout:) not sleep()
├─ Passes locally, fails CI?
│  └─ Replace sleep() with condition polling
├─ Animation causing issues?
│  └─ Wait for animation completion, don't disable
└─ Network request timing?
   └─ Use XCTestExpectation or waitForExistence

Core Pattern: Condition-Based Waiting

❌ WRONG (Arbitrary Timeout):

func testButtonAppears() {
    app.buttons["Login"].tap()
    sleep(2)  // ❌ Guessing it takes 2 seconds
    XCTAssertTrue(app.buttons["Dashboard"].exists)
}

✅ CORRECT (Wait for Condition):

func testButtonAppears() {
    app.buttons["Login"].tap()
    let dashboard = app.buttons["Dashboard"]
    XCTAssertTrue(dashboard.waitForExistence(timeout: 5))
}

Common UI Testing Patterns

Pattern 1: Waiting for Elements

// Wait for element to appear
func waitForElement(_ element: XCUIElement, timeout: TimeInterval = 5) -> Bool {
    return element.waitForExistence(timeout: timeout)
}

// Usage
XCTAssertTrue(waitForElement(app.buttons["Submit"]))

Pattern 2: Waiting for Element to Disappear

func waitForElementToDisappear(_ element: XCUIElement, timeout: TimeInterval = 5) -> Bool {
    let predicate = NSPredicate(format: "exists == false")
    let expectation = XCTNSPredicateExpectation(predicate: predicate, object: element)
    let result = XCTWaiter().wait(for: [expectation], timeout: timeout)
    return result == .completed
}

// Usage
XCTAssertTrue(waitForElementToDisappear(app.activityIndicators["Loading"]))

Pattern 3: Waiting for Specific State

func waitForButton(_ button: XCUIElement, toBeEnabled enabled: Bool, timeout: TimeInterval = 5) -> Bool {
    let predicate = NSPredicate(format: "isEnabled == %@", NSNumber(value: enabled))
    let expectation = XCTNSPredicateExpectation(predicate: predicate, object: button)
    let result = XCTWaiter().wait(for: [expectation], timeout: timeout)
    return result == .completed
}

// Usage
let submitButton = app.buttons["Submit"]
XCTAssertTrue(waitForButton(submitButton, toBeEnabled: true))
submitButton.tap()

Pattern 4: Accessibility Identifiers

Set in app:

Button("Submit") {
    // action
}
.accessibilityIdentifier("submitButton")

Use in tests:

func testSubmitButton() {
    let submitButton = app.buttons["submitButton"]  // Uses identifier, not label
    XCTAssertTrue(submitButton.waitForExistence(timeout: 5))
    submitButton.tap()
}

Why: Accessibility identifiers don't change with localization, remain stable across UI updates.

Pattern 5: Network Request Delays

func testDataLoads() {
    app.buttons["Refresh"].tap()

    // Wait for loading indicator to disappear
    let loadingIndicator = app.activityIndicators["Loading"]
    XCTAssertTrue(waitForElementToDisappear(loadingIndicator, timeout: 10))

    // Now verify data loaded
    XCTAssertTrue(app.cells.count > 0)
}

Pattern 6: Animation Handling

func testAnimatedTransition() {
    app.buttons["Next"].tap()

    // Wait for destination view to appear
    let destinationView = app.otherElements["DestinationView"]
    XCTAssertTrue(destinationView.waitForExistence(timeout: 2))

    // Optional: Wait a bit more for animation to settle
    // Only if absolutely necessary
    RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.3))
}

Testing Checklist

Before Writing Tests

• Use accessibility identifiers for all interactive elements
• Avoid hardcoded labels (use identifiers instead)
• Plan for network delays and animations
• Choose appropriate timeouts (2s UI, 10s network)

When Writing Tests

• Use waitForExistence() not sleep()
• Use predicates for complex conditions
• Test both success and failure paths
• Make tests independent (can run in any order)

After Writing Tests

• Run tests 10 times locally (catch flakiness)
• Run tests on slowest supported device
• Run tests in CI environment
• Check test duration (if >30s per test, optimize)

Xcode UI Testing Tips

Launch Arguments for Testing

func testExample() {
    let app = XCUIApplication()
    app.launchArguments = ["UI-Testing"]
    app.launch()
}

In app code:

if ProcessInfo.processInfo.arguments.contains("UI-Testing") {
    // Use mock data, skip onboarding, etc.
}

Faster Test Execution

override func setUpWithError() throws {
    continueAfterFailure = false  // Stop on first failure
}

Debugging Failing Tests

func testExample() {
    // Take screenshot on failure
    addUIInterruptionMonitor(withDescription: "Alert") { alert in
        alert.buttons["OK"].tap()
        return true
    }

    // Print element hierarchy
    print(app.debugDescription)
}

Common Mistakes

❌ Using sleep() for Everything

sleep(5)  // ❌ Wastes time if operation completes in 1s

❌ Not Handling Animations

app.buttons["Next"].tap()
XCTAssertTrue(app.buttons["Back"].exists)  // ❌ May fail during animation

❌ Hardcoded Text Labels

app.buttons["Submit"].tap()  // ❌ Breaks with localization

❌ Tests Depend on Each Other

// ❌ Test 2 assumes Test 1 ran first
func test1_Login() { /* ... */ }
func test2_ViewDashboard() { /* assumes logged in */ }

❌ No Timeout Strategy

element.waitForExistence(timeout: 100)  // ❌ Too long
element.waitForExistence(timeout: 0.1)  // ❌ Too short

Use appropriate timeouts:

• UI animations: 2-3 seconds
• Network requests: 10 seconds
• Complex operations: 30 seconds max

Real-World Impact

Before (using sleep()):

• Test suite: 15 minutes (waiting for worst-case)
• Flaky tests: 20% failure rate
• CI failures: 50% require retry

After (condition-based waiting):

• Test suite: 5 minutes (waits only as needed)
• Flaky tests: <2% failure rate
• CI failures: <5% require retry

Key insight Tests finish faster AND are more reliable when waiting for actual conditions instead of guessing times.

Recording UI Automation

Overview

NEW in Xcode 26: Record, replay, and review UI automation tests with video recordings.

Three Phases:

1. Record — Capture interactions (taps, swipes, hardware button presses) as Swift code
2. Replay — Run across multiple devices, languages, regions, orientations
3. Review — Watch video recordings, analyze failures, view UI element overlays

Supported Platforms: iOS, iPadOS, macOS, watchOS, tvOS, axiom-visionOS (Designed for iPad)

How UI Automation Works

Key Principles:

• UI automation interacts with your app as a person does using gestures and hardware events
• Runs completely independently from your app (app models/data not directly accessible)
• Uses accessibility framework as underlying technology
• Tells OS which gestures to perform, then waits for completion synchronously one at a time

Actions include:

• Launching your app
• Interacting with buttons and navigation
• Setting system state (Dark Mode, axiom-localization, etc.)
• Setting simulated location

Accessibility is the Foundation

Critical Understanding: Accessibility provides information directly to UI automation.

What accessibility sees:

• Element types (button, text, image, etc.)
• Labels (visible text)
• Values (current state for checkboxes, etc.)
• Frames (element positions)
• Identifiers (accessibility identifiers — NOT localized)

Best Practice: Great accessibility experience = great UI automation experience.

Preparing Your App for Recording

Step 1: Add Accessibility Identifiers

SwiftUI:

Button("Submit") {
    // action
}
.accessibilityIdentifier("submitButton")

// Make identifiers specific to instance
List(landmarks) { landmark in
    LandmarkRow(landmark)
        .accessibilityIdentifier("landmark-\(landmark.id)")
}

UIKit:

let button = UIButton()
button.accessibilityIdentifier = "submitButton"

// Use index for table cells
cell.accessibilityIdentifier = "cell-\(indexPath.row)"

Good identifiers are:

• ✅ Unique within entire app
• ✅ Descriptive of element contents
• ✅ Static (don't react to content changes)
• ✅ Not localized (same across languages)

Why identifiers matter:

• Titles/descriptions may change, identifiers remain stable
• Work across localized strings
• Uniquely identify elements with dynamic content

Pro Tip: Use Xcode coding assistant to add identifiers:

Prompt: "Add accessibility identifiers to the relevant parts of this view"

Step 2: Review Accessibility with Accessibility Inspector

Launch Accessibility Inspector:

• Xcode menu → Open Developer Tool → Accessibility Inspector
• Or: Launch from Spotlight

Features:

1. Element Inspector — List accessibility values for any view
2. Property details — Click property name for documentation
3. Platform support — Works on all Apple platforms

What to check:

• Elements have labels
• Interactive elements have types (button, not just text)
• Values set for stateful elements (checkboxes, toggles)
• Identifiers set for elements with dynamic/localized content

Sample Code Reference: Delivering an exceptional accessibility experience

Step 3: Add UI Testing Target

1. Open project settings in Xcode
2. Click "+" below targets list
3. Select UI Testing Bundle
4. Click Finish

Result: New UI test folder with template tests added to project.

Recording Interactions

Starting a Recording (Xcode 26)

1. Open UI test source file
2. Popover appears explaining how to start recording (first time only)
3. Click "Start Recording" button in editor gutter
4. Xcode builds and launches app in Simulator/device

During Recording:

• Interact with app normally (taps, swipes, text entry, etc.)
• Code representing interactions appears in source editor in real-time
• Recording updates as you type (e.g., text field entries)

Stopping Recording:

• Click "Stop Run" button in Xcode

Example Recording Session

func testCreateAustralianCollection() {
    let app = XCUIApplication()
    app.launch()

    // Tap "Collections" tab (recorded automatically)
    app.tabBars.buttons["Collections"].tap()

    // Tap "+" to add new collection
    app.navigationBars.buttons["Add"].tap()

    // Tap "Edit" button
    app.buttons["Edit"].tap()

    // Type collection name
    app.textFields.firstMatch.tap()
    app.textFields.firstMatch.typeText("Max's Australian Adventure")

    // Tap "Edit Landmarks"
    app.buttons["Edit Landmarks"].tap()

    // Add landmarks
    app.tables.cells.containing(.staticText, identifier:"Great Barrier Reef").buttons["Add"].tap()
    app.tables.cells.containing(.staticText, identifier:"Uluru").buttons["Add"].tap()

    // Tap checkmark to save
    app.navigationBars.buttons["Done"].tap()
}

Reviewing Recorded Code

After recording, review and adjust queries:

Multiple Options: Each line has dropdown showing alternative ways to address element.

Selection Recommendations:

1. For localized strings (text, button labels): Choose accessibility identifier if available
2. For deeply nested views: Choose shortest query (stays resilient as app changes)
3. For dynamic content (timestamps, temperature): Use generic query or identifier

Example:

// Recorded options for text field:
app.textFields["Collection Name"]              // ❌ Breaks if label localizes
app.textFields["collectionNameField"]          // ✅ Uses identifier
app.textFields.element(boundBy: 0)             // ✅ Position-based
app.textFields.firstMatch                      // ✅ Generic, shortest

Choose shortest, most stable query for your needs.

Adding Validations

After recording, add assertions to verify expected behavior:

Wait for Existence

// Validate collection created
let collection = app.buttons["Max's Australian Adventure"]
XCTAssertTrue(collection.waitForExistence(timeout: 5))

Wait for Property Changes

// Wait for button to become enabled
let submitButton = app.buttons["Submit"]
XCTAssertTrue(submitButton.wait(for: .enabled, toEqual: true, timeout: 5))

Combine with XCTAssert

// Fail test if element doesn't appear
let landmark = app.staticTexts["Great Barrier Reef"]
XCTAssertTrue(landmark.waitForExistence(timeout: 5), "Landmark should appear in collection")

Advanced Automation APIs

Setup Device State

override func setUpWithError() throws {
    let app = XCUIApplication()

    // Set device orientation
    XCUIDevice.shared.orientation = .landscapeLeft

    // Set appearance mode
    app.launchArguments += ["-UIUserInterfaceStyle", "dark"]

    // Simulate location
    let location = XCUILocation(location: CLLocation(latitude: 37.7749, longitude: -122.4194))
    app.launchArguments += ["-SimulatedLocation", location.description]

    app.launch()
}

Launch Arguments & Environment

func testWithMockData() {
    let app = XCUIApplication()

    // Pass arguments to app
    app.launchArguments = ["-UI-Testing", "-UseMockData"]

    // Set environment variables
    app.launchEnvironment = ["API_URL": "https://mock.api.com"]

    app.launch()
}

In app code:

if ProcessInfo.processInfo.arguments.contains("-UI-Testing") {
    // Use mock data, skip onboarding
}

Custom URL Schemes

// Open app to specific URL
let app = XCUIApplication()
app.open(URL(string: "myapp://landmark/123")!)

// Open URL with system default app (global version)
XCUIApplication.open(URL(string: "https://example.com")!)

Accessibility Audits in Tests

func testAccessibility() throws {
    let app = XCUIApplication()
    app.launch()

    // Perform accessibility audit
    try app.performAccessibilityAudit()
}

Reference: Perform accessibility audits for your app — WWDC23

Test Plans for Multiple Configurations

Test Plans let you:

• Include/exclude individual tests
• Set system settings (language, region, appearance)
• Configure test properties (timeouts, repetitions, parallelization)
• Associate with schemes for specific build settings

Creating Test Plan

1. Create new or use existing test plan
2. Add/remove tests on first screen
3. Switch to Configurations tab

Adding Multiple Languages

Configurations:
├─ English
├─ German (longer strings)
├─ Arabic (right-to-left)
└─ Hebrew (right-to-left)

Each locale = separate configuration in test plan.

Settings:

• Focused for specific locale
• Shared across all configurations

Video & Screenshot Capture

In Configurations tab:

• Capture screenshots: On/Off
• Capture video: On/Off
• Keep media: "Only failures" or "On, and keep all"

Defaults: Videos/screenshots kept only for failing runs (for review).

"On, and keep all" use cases:

• Documentation
• Tutorials
• Marketing materials

Reference: Author fast and reliable tests for Xcode Cloud — WWDC22

Replaying Tests in Xcode Cloud

Xcode Cloud = built-in service for:

• Building app
• Running tests
• Uploading to App Store
• All in cloud without using team devices

Workflow configuration:

• Same test plan used locally
• Runs on multiple devices and configurations
• Videos/results available in App Store Connect

Viewing Results:

• Xcode: Xcode Cloud section
• App Store Connect: Xcode Cloud section
• See build info, logs, failure descriptions, video recordings

Team Access: Entire team can see run history and download results/videos.

Reference: Create practical workflows in Xcode Cloud — WWDC23

Reviewing Test Results with Videos

Accessing Test Report

1. Click Test button in Xcode
2. Double-click failing run to see video + description

Features:

• Runs dropdown — Switch between video recordings of different configurations (languages, devices)
• Save video — Secondary click → Save
• Play/pause — Video playback with UI interaction overlays
• Timeline dots — UI interactions shown as dots on timeline
• Jump to failure — Click failure diamond on timeline

UI Element Overlay at Failure

At moment of failure:

• Click timeline failure point
• Overlay shows all UI elements present on screen
• Click any element to see code recommendations for addressing it
• Show All — See alternative examples

Workflow:

1. Identify what was actually present (vs what test expected)
2. Click element to get query code
3. Secondary click → Copy code
4. View Source → Go directly to test
5. Paste corrected code

Example:

// Test expected:
let button = app.buttons["Max's Australian Adventure"]

// But overlay shows it's actually text, not button:
let text = app.staticTexts["Max's Australian Adventure"] // ✅ Correct

Running Test in Different Language

Click test diamond → Select configuration (e.g., Arabic) → Watch automation run in right-to-left layout.

Validates: Same automation works across languages/layouts.

Reference: Fix failures faster with Xcode test reports — WWDC23

Recording UI Automation Checklist

Before Recording

• Add accessibility identifiers to interactive elements
• Review app with Accessibility Inspector
• Add UI Testing Bundle target to project
• Plan workflow to record (user journey)

During Recording

• Interact naturally with app
• Record complete user journeys (not individual taps)
• Check code generates as you interact
• Stop recording when workflow complete

After Recording

• Review recorded code options (dropdown on each line)
• Choose stable queries (identifiers > labels)
• Add validations (waitForExistence, XCTAssert)
• Add setup code (device state, launch arguments)
• Run test to verify it passes

Test Plan Configuration

• Create/update test plan
• Add multiple language configurations
• Include right-to-left languages (Arabic, Hebrew)
• Configure video/screenshot capture settings
• Set appropriate timeouts for network tests

Running & Reviewing

• Run test locally across configurations
• Review video recordings for failures
• Use UI element overlay to debug failures
• Run in Xcode Cloud for team visibility
• Download and share videos if needed

Network Conditioning in Tests

Overview

UI tests can pass on fast networks but fail on 3G/LTE. Network Link Conditioner simulates real-world network conditions to catch timing-sensitive crashes.

Critical scenarios:

• ❌ iPad Pro over Wi-Fi (fast) → pass
• ❌ iPad Pro over 3G (slow) → crash
• ✅ Test both to catch device-specific failures

Setup Network Link Conditioner

Install Network Link Conditioner:

1. Download from Apple's Additional Tools for Xcode
2. Search: "Network Link Conditioner"
3. Install: sudo open Network\ Link\ Conditioner.pkg

Verify Installation:

# Check if installed
ls ~/Library/Application\ Support/Network\ Link\ Conditioner/

Enable in Tests:

override func setUpWithError() throws {
    let app = XCUIApplication()

    // Launch with network conditioning argument
    app.launchArguments = ["-com.apple.CoreSimulator.CoreSimulatorService", "-networkShaping"]
    app.launch()
}

Common Network Profiles

3G Profile (most failures occur here):

override func setUpWithError() throws {
    let app = XCUIApplication()

    // Simulate 3G (type in launch arguments)
    app.launchEnvironment = [
        "SIMULATOR_UDID": ProcessInfo.processInfo.environment["SIMULATOR_UDID"] ?? "",
        "NETWORK_PROFILE": "3G"
    ]
    app.launch()
}

Manual Network Conditioning (macOS System Preferences):

1. Open System Preferences → Network
2. Click "Network Link Conditioner" (installed above)
3. Select profile: 3G, LTE, WiFi
4. Click "Start"
5. Run tests (they'll use throttled network)

Real-World Example: Photo Upload with Network Throttling

❌ Without Network Conditioning:

func testPhotoUpload() {
    app.buttons["Upload Photo"].tap()

    // Passes locally (fast network)
    XCTAssertTrue(app.staticTexts["Upload complete"].waitForExistence(timeout: 5))
}
// ✅ Passes locally, ❌ FAILS on 3G with timeout

✅ With Network Conditioning:

func testPhotoUploadOn3G() {
    let app = XCUIApplication()
    // Network Link Conditioner running (3G profile)
    app.launch()

    app.buttons["Upload Photo"].tap()

    // Increase timeout for 3G
    XCTAssertTrue(app.staticTexts["Upload complete"].waitForExistence(timeout: 30))

    // Verify no crash occurred
    XCTAssertFalse(app.alerts.element.exists, "App should not crash on 3G")
}

Key differences:

• Longer timeout (30s instead of 5s)
• Check for crashes
• Run on slowest expected network

Multi-Factor Testing: Device Size + Network Speed

The Problem

Tests can pass on device A but fail on device B due to layout differences + network delays. Multi-factor testing catches these combinations.

Common failure patterns:

• ✅ iPhone 14 Pro (compact, fast network)
• ❌ iPad Pro 12.9 (large, 3G network) → crashes
• ✅ iPhone 15 (compact, LTE)
• ❌ iPhone 12 (older GPU, 3G) → timeout

Test Plan Configuration for Multiple Devices

Create Test Plan in Xcode:

1. File → New → Test Plan
2. Select tests to include
3. Click "Configurations" tab
4. Add configurations for each device/network combo

Example Configuration Matrix:

Configurations:
├─ iPhone 14 Pro + LTE
├─ iPhone 14 Pro + 3G
├─ iPad Pro 12.9 + LTE
├─ iPad Pro 12.9 + 3G  (⚠️ Most failures here)
└─ iPhone 12 + 3G      (⚠️ Older device)

In Test Plan UI:

• Device: iPhone 14 Pro / iPad Pro 12.9
• OS Version: Latest
• Locale: English
• Network Profile: LTE / 3G

Programmatic Device-Specific Testing

import XCTest

final class MultiFactorUITests: XCTestCase {
    var deviceModel: String { UIDevice.current.model }

    override func setUpWithError() throws {
        let app = XCUIApplication()
        app.launch()

        // Adjust timeouts based on device
        switch deviceModel {
        case "iPad" where UIScreen.main.bounds.width > 1000:
            // iPad Pro - larger layout, slower rendering
            app.launchEnvironment["TEST_TIMEOUT"] = "30"
        case "iPhone":
            // iPhone - compact, standard timeout
            app.launchEnvironment["TEST_TIMEOUT"] = "10"
        default:
            app.launchEnvironment["TEST_TIMEOUT"] = "15"
        }
    }

    func testListLoadingAcrossDevices() {
        let app = XCUIApplication()
        let timeout = Double(app.launchEnvironment["TEST_TIMEOUT"] ?? "10") ?? 10

        app.buttons["Refresh"].tap()

        // Wait for list to load (timeout varies by device)
        XCTAssertTrue(
            app.tables.cells.count > 0,
            "List should load on \(deviceModel)"
        )

        // Verify no crashes
        XCTAssertFalse(app.alerts.element.exists)
    }
}

Real-World Example: iPad Pro + 3G Crash

Scenario: App works on iPhone 14, crashes on iPad Pro over 3G.

Why it crashes:

1. iPad Pro has larger layout (landscape)
2. 3G network is slow (latency 100ms+)
3. Images don't load in time, layout engine crashes
4. Single-device testing misses this combo

Test that catches it:

func testLargeLayoutOn3G() {
    let app = XCUIApplication()
    // Running with Network Link Conditioner on 3G profile
    app.launch()

    // iPad Pro: Large grid of images
    app.buttons["Browse"].tap()

    // Wait longer for images on slow network
    let firstImage = app.images["photoGrid-0"]
    XCTAssertTrue(
        firstImage.waitForExistence(timeout: 20),
        "First image must load on slow network"
    )

    // Verify grid loaded without crash
    let loadedCount = app.images.matching(identifier: NSPredicate(format: "identifier BEGINSWITH 'photoGrid'")).count
    XCTAssertGreater(loadedCount, 5, "Multiple images should load on 3G")

    // No alerts (no crashes)
    XCTAssertFalse(app.alerts.element.exists, "App should not crash on large device + slow network")
}

Running Multi-Factor Tests in CI

In GitHub Actions or Xcode Cloud:

- name: Run tests across devices
  run: |
    xcodebuild -scheme MyApp \
      -testPlan MultiDeviceTestPlan \
      test

Test Plan runs on:

• iPhone 14 Pro + LTE
• iPhone 14 Pro + 3G
• iPad Pro + LTE
• iPad Pro + 3G

Result: Catch device-specific crashes before App Store submission.

Debugging Crashes Revealed by UI Tests

Overview

UI tests sometimes reveal crashes that don't happen in manual testing. Key insight Automated tests run faster, interact with app differently, and can expose concurrency/timing bugs.

When crashes happen:

• ❌ Manual testing: Can't reproduce (works when you run it)
• ✅ UI Test: Crashes every time (automated repetition finds race condition)

Recognizing Test-Revealed Crashes

Signs in test output:

Failing test: testPhotoUpload
Error: The app crashed while responding to a UI event
App died from an uncaught exception
Stack trace: [EXC_BAD_ACCESS in PhotoViewController]

Video shows: App visibly crashes (black screen, immediate termination).

Systematic Debugging Approach

Step 1: Capture Crash Details

Enable detailed logging:

override func setUpWithError() throws {
    let app = XCUIApplication()

    // Enable all logging
    app.launchEnvironment = [
        "OS_ACTIVITY_MODE": "debug",
        "DYLD_PRINT_STATISTICS": "1"
    ]

    // Enable test diagnostics
    if #available(iOS 17, *) {
        let options = XCUIApplicationLaunchOptions()
        options.captureRawLogs = true
        app.launch(options)
    } else {
        app.launch()
    }
}

Step 2: Reproduce Locally

func testReproduceCrash() {
    let app = XCUIApplication()
    app.launch()

    // Run exact sequence that causes crash
    app.buttons["Browse"].tap()
    app.buttons["Photo Album"].tap()
    app.buttons["Select All"].tap()
    app.buttons["Upload"].tap()

    // Should crash here
    let uploadButton = app.buttons["Upload"]
    XCTAssertFalse(uploadButton.exists, "App crashed (expected)")

    // Don't assert - just let it crash and read logs
}

Run test with Console logs visible:

• Xcode: View → Navigators → Show Console
• Watch for exception messages

Step 3: Analyze Crash Logs

Locations:

1. Xcode Console (real-time, less detail)
2. ~/Library/Logs/DiagnosticMessages/crash_*.log (full details)
3. Device Settings → Privacy → Analytics → Analytics Data

Look for:

• Thread that crashed
• Exception type (EXC_BAD_ACCESS, EXC_CRASH, etc.)
• Stack trace showing which method crashed

Example crash log:

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000
Thread 0 Crashed:
0  MyApp    0x0001a234 -[PhotoViewController reloadPhotos:] + 234
1  MyApp    0x0001a123 -[PhotoViewController viewDidLoad] + 180

This tells us:

• Crash in PhotoViewController.reloadPhotos(_:)
• Likely null pointer dereference
• Called from viewDidLoad

Step 4: Connection to Swift Concurrency Issues

Most UI test crashes are concurrency bugs (not specific to UI testing). Reference related skills:

// Common pattern: Race condition in async image loading
class PhotoViewController: UIViewController {
    var photos: [Photo] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        // ❌ WRONG: Accessing photos array from multiple threads
        Task {
            let newPhotos = await fetchPhotos()
            self.photos = newPhotos  // May crash if main thread access
            reloadPhotos()  // ❌ Crash here
        }
    }
}

// ✅ CORRECT: Ensure main thread
class PhotoViewController: UIViewController {
    @MainActor
    var photos: [Photo] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        Task {
            let newPhotos = await fetchPhotos()
            await MainActor.run { [weak self] in
                self?.photos = newPhotos
                self?.reloadPhotos()  // ✅ Safe
            }
        }
    }
}

For deep crash analysis: See axiom-swift-concurrency skill for @MainActor patterns and axiom-memory-debugging skill for thread-safety issues.

Step 5: Add Crash-Prevention Tests

After fixing:

func testPhotosLoadWithoutCrash() {
    let app = XCUIApplication()
    app.launch()

    // Rapid fire interactions that previously caused crash
    app.buttons["Browse"].tap()
    app.buttons["Photo Album"].tap()

    // Load should complete without crash
    let photoGrid = app.otherElements["photoGrid"]
    XCTAssertTrue(photoGrid.waitForExistence(timeout: 10))

    // No alerts (no crash dialogs)
    XCTAssertFalse(app.alerts.element.exists)
}

Step 6: Stress Test to Verify Fix

func testPhotosLoadUnderStress() {
    let app = XCUIApplication()
    app.launch()

    // Repeat the crash-causing action multiple times
    for iteration in 0..<10 {
        app.buttons["Browse"].tap()

        // Wait for load
        let grid = app.otherElements["photoGrid"]
        XCTAssertTrue(grid.waitForExistence(timeout: 10), "Iteration \(iteration)")

        // Go back
        app.navigationBars.buttons["Back"].tap()
        app.buttons["Refresh"].tap()
    }

    // Completed without crash
    XCTAssertTrue(true, "Stress test passed")
}

Prevention Checklist

Before releasing

• Run UI tests on slowest network (3G)
• Run on largest device (iPad Pro)
• Run on oldest supported device (iPhone 12)
• Record video of test runs (saves debugging time)
• Check for crashes in logs
• Run stress tests (10x repeated actions)
• Verify @MainActor on UI properties
• Check for race conditions in async code

Resources

WWDC: 2025-344, 2024-10179, 2023-10175, 2023-10035

Docs: /xctest, /xcuiautomation/recording-ui-automation-for-testing, /xctest/xctwaiter, /accessibility/delivering_an_exceptional_accessibility_experience, /accessibility/performing_accessibility_testing_for_your_app

Note: This skill focuses on reliability patterns and Recording UI Automation. For TDD workflow, see superpowers:test-driven-development.

History: See git log for changes