React Native Testing

React Native Testing Skill

Learn comprehensive testing strategies including unit tests, component tests, and E2E tests.

Prerequisites

• React Native basics
• Understanding of async/await
• Familiarity with testing concepts

Learning Objectives

After completing this skill, you will be able to:

• [ ] Configure Jest for React Native
• [ ] Write component tests with Testing Library
• [ ] Mock native modules and APIs
• [ ] Implement E2E tests with Detox/Maestro
• [ ] Set up CI/CD test pipelines

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Topics Covered

1. Jest Setup

// jest.config.js
module.exports = {
  preset: 'react-native',
  setupFilesAfterEnv: ['@testing-library/jest-native/extend-expect'],
  transformIgnorePatterns: [
    'node_modules/(?!(react-native|@react-native)/)',
  ],
};

2. Component Testing

import { render, screen, fireEvent } from '@testing-library/react-native';
import { Button } from './Button';

describe('Button', () => {
  it('calls onPress when pressed', () => {
    const onPress = jest.fn();
    render(<Button title="Click" onPress={onPress} />);

    fireEvent.press(screen.getByText('Click'));

    expect(onPress).toHaveBeenCalled();
  });
});

3. Hook Testing

import { renderHook, act } from '@testing-library/react-native';
import { useCounter } from './useCounter';

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

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

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

4. Mocking

// Mock native module
jest.mock('@react-native-async-storage/async-storage', () => ({
  setItem: jest.fn(),
  getItem: jest.fn(),
}));

// Mock API
jest.mock('./api', () => ({
  fetchUser: jest.fn().mockResolvedValue({ id: '1', name: 'Test' }),
}));

5. E2E with Detox

describe('Login', () => {
  beforeAll(async () => {
    await device.launchApp();
  });

  it('should login successfully', async () => {
    await element(by.id('email')).typeText('test@example.com');
    await element(by.id('password')).typeText('password');
    await element(by.id('login-btn')).tap();

    await expect(element(by.id('home'))).toBeVisible();
  });
});

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Quick Start Example

// ProductCard.test.tsx
import { render, screen, fireEvent } from '@testing-library/react-native';
import { ProductCard } from './ProductCard';

const mockProduct = {
  id: '1',
  title: 'Test Product',
  price: 99.99,
};

describe('ProductCard', () => {
  it('renders product info', () => {
    render(<ProductCard {...mockProduct} onPress={jest.fn()} />);

    expect(screen.getByText('Test Product')).toBeOnTheScreen();
    expect(screen.getByText('$99.99')).toBeOnTheScreen();
  });

  it('handles press', () => {
    const onPress = jest.fn();
    render(<ProductCard {...mockProduct} onPress={onPress} />);

    fireEvent.press(screen.getByRole('button'));

    expect(onPress).toHaveBeenCalledWith('1');
  });
});

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Common Errors & Solutions

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Validation Checklist

• [ ] Unit tests pass
• [ ] Component tests cover interactions
• [ ] E2E tests complete flows
• [ ] Coverage meets threshold (80%+)

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Usage

Skill("react-native-testing")

Bonded Agent: 06-react-native-testing

React Native Testing Guide

Overview

This guide provides comprehensive documentation for the react-native-testing skill in the custom-plugin-react-native plugin.

Category: Testing

Quick Start

Prerequisites

• Familiarity with testing concepts
• Development environment set up
• Plugin installed and configured

Basic Usage

# Invoke the skill
claude "react-native-testing - [your task description]"

# Example
claude "react-native-testing - analyze the current implementation"

Core Concepts

Key Principles

1. Consistency - Follow established patterns 2. Clarity - Write readable, maintainable code 3. Quality - Validate before deployment

Best Practices

• Always validate input data
• Handle edge cases explicitly
• Document your decisions
• Write tests for critical paths

Common Tasks

Task 1: Basic Implementation

# Example implementation pattern
def implement_react_native_testing(input_data):
    """
    Implement react-native-testing functionality.

    Args:
        input_data: Input to process

    Returns:
        Processed result
    """
    # Validate input
    if not input_data:
        raise ValueError("Input required")

    # Process
    result = process(input_data)

    # Return
    return result

Task 2: Advanced Usage

For advanced scenarios, consider:

• Configuration customization via assets/config.yaml
• Validation using scripts/validate.py
• Integration with other skills

Troubleshooting

Common Issues

Related Resources

• SKILL.md - Skill specification
• config.yaml - Configuration options
• validate.py - Validation script

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Last updated: 2025-12-30

React Native Testing Patterns

Design Patterns

Pattern 1: Input Validation

Always validate input before processing:

def validate_input(data):
    if data is None:
        raise ValueError("Data cannot be None")
    if not isinstance(data, dict):
        raise TypeError("Data must be a dictionary")
    return True

Pattern 2: Error Handling

Use consistent error handling:

try:
    result = risky_operation()
except SpecificError as e:
    logger.error(f"Operation failed: {e}")
    handle_error(e)
except Exception as e:
    logger.exception("Unexpected error")
    raise

Pattern 3: Configuration Loading

Load and validate configuration:

import yaml

def load_config(config_path):
    with open(config_path) as f:
        config = yaml.safe_load(f)
    validate_config(config)
    return config

Anti-Patterns to Avoid

❌ Don't: Swallow Exceptions

# BAD
try:
    do_something()
except:
    pass

✅ Do: Handle Explicitly

# GOOD
try:
    do_something()
except SpecificError as e:
    logger.warning(f"Expected error: {e}")
    return default_value

Category-Specific Patterns: Testing

Recommended Approach

1. Start with the simplest implementation 2. Add complexity only when needed 3. Test each addition 4. Document decisions

Common Integration Points

• Configuration: assets/config.yaml
• Validation: scripts/validate.py
• Documentation: references/GUIDE.md

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Pattern library for react-native-testing skill