Detox Setup and First React Native Test

1Layer          Tool                          Speed   Fidelity
2Unit           Jest + @testing-library/rn    Fast    Low
3Component      Jest + @testing-library/rn    Fast    Medium
4E2E (gray-box) Detox                         Slow    High
5E2E (black-box) Appium                       Slow    High
6Performance    Flashlight + Detox            Slow    High

1# Install @testing-library/react-native
2npm install --save-dev @testing-library/react-native @testing-library/jest-native
3
4# Install Detox
5npm install --save-dev detox
6npx detox init
7
8# Build and run Detox tests:
9npx detox build --configuration ios.sim.debug
10npx detox test --configuration ios.sim.debug

1import { render, screen, fireEvent } from '@testing-library/react-native';
2
3test('renders and handles interaction', () => {
4  const onPress = jest.fn();
5  render(<EnrollButton courseId="c1" onEnroll={onPress} />);
6
7  const button = screen.getByRole('button', { name: /enroll/i });
8  fireEvent.press(button);
9  expect(onPress).toHaveBeenCalledWith('c1');
10});
11
12test('shows loading state during enrollment', async () => {
13  render(<EnrollButton courseId="c1" isLoading onEnroll={jest.fn()} />);
14  expect(screen.getByRole('progressbar')).toBeTruthy();
15  expect(screen.getByRole('button')).toBeDisabled();
16});

1import { device, element, by, expect as detoxExpect } from 'detox';
2
3describe('Login E2E', () => {
4  beforeAll(async () => await device.launchApp({ newInstance: true }));
5
6  it('completes login flow', async () => {
7    await element(by.id('email-input')).typeText('[email protected]');
8    await element(by.id('password-input')).typeText('Pass123!');
9    await element(by.id('password-input')).tapReturnKey();
10    await detoxExpect(element(by.id('dashboard-screen'))).toBeVisible();
11  });
12
13  it('shows error on invalid credentials', async () => {
14    await device.reloadReactNative();
15    await element(by.id('email-input')).typeText('[email protected]');
16    await element(by.id('password-input')).typeText('WrongPass');
17    await element(by.id('login-button')).tap();
18    await detoxExpect(element(by.id('error-message'))).toBeVisible();
19  });
20});

1// Test orientation changes
2await device.setOrientation('landscape');
3await detoxExpect(element(by.id('courses-list'))).toBeVisible();
4await device.setOrientation('portrait');
5
6// Test biometric authentication
7await device.setBiometricEnrollment(true);
8await element(by.id('use-face-id-button')).tap();
9await device.matchFace();
10await detoxExpect(element(by.id('dashboard-screen'))).toBeVisible();
11
12// Take screenshot for visual comparison
13await device.takeScreenshot('login-screen');
14
15// Test with slow network (3G simulation)
16await device.setStatusBar({ network: 'hsdpa' }); // 3G-ish
17await element(by.id('courses-tab')).tap();
18// Verify loading state appears
19await detoxExpect(element(by.id('loading-spinner'))).toBeVisible();

1# GitHub Actions for React Native
2jobs:
3  unit-tests:
4    runs-on: ubuntu-latest
5    steps:
6      - uses: actions/checkout@v4
7      - run: npm ci && npm test -- --ci --coverage
8
9  e2e-ios:
10    runs-on: macos-latest  # Required for iOS simulator
11    steps:
12      - uses: actions/checkout@v4
13      - run: npm ci
14      - run: cd ios && pod install
15      - run: npx detox build --configuration ios.sim.debug
16      - run: npx detox test --configuration ios.sim.debug --headless
17      - uses: actions/upload-artifact@v4
18        if: always()
19        with: { name: detox-results, path: artifacts/ }