Add unit testing framework with Jest and React Testing Library

[bigweavergammainternal]

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Summary

This PR establishes a comprehensive unit testing framework for the amplify-next-template repository using Jest and React Testing Library, specifically configured for Next.js 14 applications. The implementation provides a solid foundation for maintaining code quality and ensuring component reliability through automated testing.

Configuration Files Added:

• jest.config.js - Jest configuration using Next.js's built-in Jest support

  • Configured test environment as jsdom for React component testing
  • Module path alias mapping for @/ imports
  • Exclusion patterns for node_modules, .next, and amplify directories
  • Coverage collection settings for app directory

• jest.setup.js - Jest setup file with essential mocks

  • Integration with @testing-library/jest-dom for extended matchers
  • Mock for next/font/google (Inter font)
  • Mock for aws-amplify configuration
  • Mock for aws-amplify/data with generateClient functionality
  • Mock for @aws-amplify/ui-react/styles.css
  • Mock for amplify_outputs.json configuration
  • Mock for window.prompt browser API

Test Files Added:

• __tests__/page.test.tsx - Tests for the main page component (app/page.tsx)

  • Rendering tests: heading, button, success message, tutorial link, empty todo list
  • Todo list subscription tests: mount subscription, data display, key rendering
  • Create todo functionality tests: prompt interaction, create with content, cancel handling
  • Accessibility tests: main landmark, heading hierarchy

• __tests__/layout.test.tsx - Tests for the root layout component (app/layout.tsx)

  • Rendering tests: children rendering, html lang attribute, body with font class
  • Multiple children handling tests
  • Metadata export tests: title, description validation
  • Accessibility tests: document structure, language attribute

Test Scripts Added:

• test - Run all tests: jest
• test:watch - Run tests in watch mode: jest --watch
• test:coverage - Run tests with coverage report: jest --coverage

Dependencies Added:

• jest@^29.7.0 - JavaScript testing framework
• jest-environment-jsdom@^29.7.0 - JSDOM environment for browser-like testing
• ts-jest@^29.2.5 - TypeScript preprocessor for Jest
• @testing-library/react@^16.0.1 - React component testing utilities
• @testing-library/jest-dom@^6.5.0 - Custom Jest matchers for DOM assertions
• @types/jest@^29.5.13 - TypeScript definitions for Jest

######[This description was generated by Claude]