React Native Module 9: Testing and Debugging – Ensure App Quality

Module 9: Testing and Debugging

Course Overview: This module covers testing and debugging in React Native. You will learn unit testing, integration testing, debugging tools, and strategies to identify and fix errors efficiently to ensure stable and high-quality mobile applications.

✅ Unit Testing with Jest

Unit tests verify the functionality of individual components or functions. React Native integrates seamlessly with Jest.

Install Jest:

npm install --save-dev jest
npm install --save-dev @testing-library/react-native

Example: Testing a simple component:

import React from 'react';
import { render } from '@testing-library/react-native';
import MyComponent from '../MyComponent';

test('renders correct text', () => {
  const { getByText } = render(<MyComponent title="Hello" />);
  expect(getByText('Hello')).toBeTruthy();
});

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✅ Integration Testing

Integration tests check if multiple components work together correctly.

Example: Testing navigation:

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

test('navigates to details screen', () => {
  const { getByText } = render(<App />);
  fireEvent.press(getByText('Go to Details'));
  expect(getByText('Details Screen')).toBeTruthy();
});

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✅ Debugging Tools

Debugging helps identify and fix errors in React Native apps.

Popular debugging tools:

• React Native Debugger: Standalone app integrating Redux DevTools and Chrome DevTools.
• Flipper: Official debugging tool for React Native with network, layout, and performance inspection.
• Console Logging: Simple and effective for small apps; use console.log(), console.warn(), and console.error().

Example: Using React Native Debugger:

1. Start React Native Debugger.
2. Open your app on simulator or device.
3. Shake device (or Ctrl+M / Cmd+M) and enable "Debug JS Remotely".
4. Inspect network calls, component hierarchy, and Redux state.

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✅ Common Debugging Tips

• Check the simulator/device logs using npx react-native log-android or log-ios.
• Break down large components into smaller ones to isolate issues.
• Use error boundaries to catch runtime errors in UI components.
• Validate props with PropTypes to catch type-related bugs.
• Regularly run automated tests to prevent regressions.

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✅ Summary

• Unit testing ensures individual components function correctly.
• Integration testing verifies components work together.
• React Native Debugger and Flipper provide powerful inspection tools.
• Console logging and error boundaries help identify runtime issues.
• Testing and debugging are crucial for reliable, maintainable, and high-quality React Native apps.