mobile-testing

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Mobile Testing

Mobile testing covers the end-to-end quality pipeline for native and hybrid mobile applications - from writing automated UI tests with Detox and Appium, to running them across real device farms, to capturing crashes in production and distributing beta builds for human verification. Unlike web testing, mobile testing must deal with platform fragmentation (iOS/Android), device-specific behavior, app lifecycle events, permissions dialogs, and binary distribution gatekeeping by Apple and Google.

When to use this skill

Trigger this skill when the user:

• Wants to write or debug a Detox e2e test for a React Native app
• Needs to set up Appium for native iOS or Android test automation
• Asks about running tests on AWS Device Farm, Firebase Test Lab, or BrowserStack
• Wants to configure crash reporting with Crashlytics, Sentry, or Bugsnag
• Needs to distribute beta builds via TestFlight, Firebase App Distribution, or App Center
• Asks about device matrix strategies or test sharding across real devices
• Wants to symbolicate crash reports or set up dSYM/ProGuard mapping uploads
• Is building a mobile CI/CD pipeline that includes automated testing and distribution

Do NOT trigger this skill for:

• Web browser testing with Cypress, Playwright, or Selenium (those are web-specific)
• React Native development questions unrelated to testing or distribution

Key principles

1. Test on real devices, not just simulators - Simulators miss touch latency, GPS

drift, camera behavior, memory pressure, and thermal throttling. Use simulators for fast feedback during development, but gate releases on real-device test runs via device farms.

1. Separate test layers by speed - Unit tests (Jest/XCTest) run in milliseconds

and cover logic. Integration tests verify module boundaries. E2e tests (Detox/Appium) are slow and flaky by nature - reserve them for critical user journeys only (login, purchase, onboarding). The pyramid still applies: many unit, fewer integration, fewest e2e.

1. Treat crash reporting as a first-class signal - Ship no build without crash

reporting wired. Upload dSYMs and ProGuard mappings in CI, not manually. Monitor crash-free rate as a release gate - below 99.5% should block rollout.

1. Automate beta distribution in CI - Never distribute builds manually. Every

merge to a release branch should trigger: build, test on device farm, upload to beta channel, notify testers. Manual uploads break traceability and invite version confusion.

1. Pin device matrices and OS versions - Define an explicit device/OS matrix in

your CI config. Test against the minimum supported OS, the latest OS, and 1-2 popular mid-range devices. Do not test against "all devices" - it is slow, expensive, and the tail adds almost no signal.

Core concepts

Detox vs Appium - Detox is a gray-box testing framework built for React Native. It synchronizes with the app's JS thread and native UI, eliminating most timing-related flakiness. Appium is a black-box, cross-platform tool that uses the WebDriver protocol to drive native apps, hybrid apps, or mobile web. Use Detox for React Native projects (faster, less flaky). Use Appium when testing truly native apps (Swift/Kotlin) or when you need cross-platform parity from a single test suite.

Device farms - Cloud services that maintain pools of real physical devices. You upload your app binary and test suite, the farm runs tests across your chosen device matrix, and returns results with logs, screenshots, and video. AWS Device Farm, Firebase Test Lab, and BrowserStack App Automate are the major players. They differ in device availability, pricing model, and integration depth with their respective ecosystems.

Crash reporting pipeline - The SDK (Crashlytics, Sentry, Bugsnag) captures uncaught exceptions and native signals (SIGSEGV, SIGABRT) at runtime. Raw crash logs contain only memory addresses. Symbolication maps these addresses back to source file names and line numbers using debug symbols (dSYMs for iOS, ProGuard/R8 mapping files for Android). Without symbolication, crash reports are unreadable.

Beta distribution - Getting pre-release builds to internal testers and external beta users. Apple requires TestFlight for iOS (with mandatory App Store Connect processing). Android is more flexible - Firebase App Distribution, direct APK/AAB sharing, or Play Console internal tracks all work. Each channel has different compliance requirements, device limits, and approval latencies.

Common tasks

Write a Detox e2e test for React Native

Detox tests use element matchers, actions, and expectations. The test synchronizes automatically with animations and network calls.

// e2e/login.test.js
describe('Login flow', () => {
  beforeAll(async () => {
    await device.launchApp({ newInstance: true });
  });

  beforeEach(async () => {
    await device.reloadReactNative();
  });

  it('should login with valid credentials', async () => {
    await element(by.id('email-input')).typeText('user@example.com');
    await element(by.id('password-input')).typeText('password123');
    await element(by.id('login-button')).tap();
    await expect(element(by.id('dashboard-screen'))).toBeVisible();
  });

  it('should show error on invalid credentials', async () => {
    await element(by.id('email-input')).typeText('wrong@example.com');
    await element(by.id('password-input')).typeText('bad');
    await element(by.id('login-button')).tap();
    await expect(element(by.text('Invalid credentials'))).toBeVisible();
  });
});

Always use testID props in React Native components and match with by.id().

Never match by text for interactive elements - text changes with i18n.

Configure Appium for a native Android test

// wdio.conf.js (WebdriverIO + Appium)
exports.config = {
  runner: 'local',
  port: 4723,
  path: '/wd/hub',
  specs: ['./test/specs/**/*.js'],
  capabilities: [{
    platformName: 'Android',
    'appium:deviceName': 'Pixel 6',
    'appium:platformVersion': '13.0',
    'appium:automationName': 'UiAutomator2',
    'appium:app': './app/build/outputs/apk/debug/app-debug.apk',
    'appium:noReset': false,
  }],
  framework: 'mocha',
  mochaOpts: { timeout: 120000 },
};

// test/specs/login.spec.js
describe('Login', () => {
  it('should authenticate successfully', async () => {
    const emailField = await $('~email-input');
    await emailField.setValue('user@example.com');
    const passwordField = await $('~password-input');
    await passwordField.setValue('password123');
    const loginBtn = await $('~login-button');
    await loginBtn.click();
    const dashboard = await $('~dashboard-screen');
    await expect(dashboard).toBeDisplayed();
  });
});

Run tests on AWS Device Farm

# buildspec.yml for AWS Device Farm via CodeBuild
version: 0.2
phases:
  build:
    commands:
      - npm run build:android
      - |
        aws devicefarm schedule-run \
          --project-arn "arn:aws:devicefarm:us-west-2:123456789:project/abc" \
          --app-arn "$(aws devicefarm create-upload \
            --project-arn $PROJECT_ARN \
            --name app.apk \
            --type ANDROID_APP \
            --query 'upload.arn' --output text)" \
          --device-pool-arn "$DEVICE_POOL_ARN" \
          --test type=APPIUM_NODE,testPackageArn="$TEST_PACKAGE_ARN"

Run tests on Firebase Test Lab

# Upload and run instrumented tests on Firebase Test Lab
gcloud firebase test android run \
  --type instrumentation \
  --app app/build/outputs/apk/debug/app-debug.apk \
  --test app/build/outputs/apk/androidTest/debug/app-debug-androidTest.apk \
  --device model=Pixel6,version=33,locale=en,orientation=portrait \
  --device model=Pixel4a,version=30,locale=en,orientation=portrait \
  --timeout 10m \