device-testing

# Device Testing Expert

Comprehensive expertise in React Native testing strategies, from unit tests to end-to-end testing on real devices and simulators. Specializes in Jest, Detox, React Native Testing Library, and mobile testing best practices.

## What I Know

### Testing Pyramid for Mobile

**Three Layers**
1. **Unit Tests** (70%): Fast, isolated, test logic
2. **Integration Tests** (20%): Test component integration
3. **E2E Tests** (10%): Test full user flows on devices

**Tools**
- **Jest**: Unit and integration testing
- **React Native Testing Library**: Component testing
- **Detox**: E2E testing on simulators/emulators
- **Maestro**: Alternative E2E testing (newer)

### Unit Testing with Jest

**Basic Component Test**
```javascript
// UserProfile.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import UserProfile from './UserProfile';

describe('UserProfile', () => {
  it('renders user name correctly', () => {
    const user = { name: 'John Doe', email: 'john@example.com' };
    const { getByText } = render(<UserProfile user={user} />);

    expect(getByText('John Doe')).toBeTruthy();
    expect(getByText('john@example.com')).toBeTruthy();
  });

  it('calls onPress when button is pressed', () => {
    const onPress = jest.fn();
    const { getByText } = render(
      <UserProfile user={{ name: 'John' }} onPress={onPress} />
    );

    fireEvent.press(getByText('Edit Profile'));
    expect(onPress).toHaveBeenCalledTimes(1);
  });
});
```

**Testing Hooks**
```javascript
// useCounter.test.js
import { renderHook, act } from '@testing-library/react-hooks';
import useCounter from './useCounter';

describe('useCounter', () => {
  it('increments counter', () => {
    const { result } = renderHook(() => useCounter());

    act(() => {
      result.current.increment();
    });

    expect(result.current.count).toBe(1);
  });

  it('decrements counter', () => {
    const { result } = renderHook(() => useCounter(