Octocode MCP

# Testing Best Practices Resources > Testing strategies, frameworks, and best practices for Node.js/TypeScript applications ** Purpose:** Testing resources for AI agents building Node.js/TypeScript applications **🌐 Focus:** Vitest, Jest, Playwright - JavaScript/TypeScript testing **⚙️ Runtime:** All tests run on Node.js (unit, integration, E2E) **📅 Updated:** October 13, 2025 --- ## Quick Reference ### Best Practices (Must-Read) - **Essential Guide:** `goldbergyoni/javascript-testing-best-practices` (25K+ ⭐) - Complete JS testing guide - **Node.js Advanced:** `goldbergyoni/nodejs-testing-best-practices` (4K+ ⭐) - Advanced patterns - **Enforce Best Practices:** `testing-library/eslint-plugin-testing-library` (1K+ ⭐) - ESLint rules ### Unit Testing Frameworks - **Modern (2025 Default):** `vitest-dev/vitest` (12K+ ⭐) - Vite-powered, fast, ESM-native - **Industry Standard:** `jestjs/jest` (44K+ ⭐) - Mature, 40M+ weekly downloads - **Choose Vitest for:** New projects, Vite apps, modern ESM/TypeScript - **Choose Jest for:** React Native, legacy codebases, existing Jest projects ### E2E Testing - **Best Overall:** `microsoft/playwright` (73K+ ⭐) - Cross-browser, fast, reliable - **Alternative:** `cypress-io/cypress` (48K+ ⭐) - Developer-friendly, great DX - **Choose Playwright for:** Cross-browser, parallel execution, best performance - **Choose Cypress for:** Quick setup, excellent dev experience, simpler API ### React Testing - **User-Centric:** `testing-library/react-testing-library` (19K+ ⭐) - Test like users - **React Native:** `callstack/react-native-testing-library` (4K+ ⭐) - Same patterns for mobile - **Mobile E2E:** `wix/Detox` (12K+ ⭐) - Gray box testing for React Native ### Mocking & Utilities - **API Mocking:** `mswjs/msw` (17K+ ⭐) - Mock by intercepting requests - **Test Doubles:** `sinonjs/sinon` (10K+ ⭐) - Spies, stubs, mocks - **Fake Data:** `faker-js/faker` (14K+ ⭐) - Generate realistic test data ### Decision Guide | Need | Choose | Why | |------|--------|-----| | Unit Tests (New) | Vitest | Fast, ESM-native, Vite-powered | | Unit Tests (Legacy) | Jest | Mature, React Native support | | E2E Tests | Playwright | Cross-browser, parallel, reliable | | React Testing | React Testing Library | User-centric, best practices | | API Mocking | MSW | Intercept at network level | | Mobile E2E | Detox | Gray box for React Native | --- ## Best Practices (Essential Reading) **⭐ goldbergyoni/javascript-testing-best-practices** (25K+ ⭐) ⚡ ESSENTIAL - 🔗 https://github.com/goldbergyoni/javascript-testing-best-practices - Complete JavaScript & Node.js testing best practices (August 2025) **⭐ goldbergyoni/nodejs-testing-best-practices** (4K+ ⭐) - 🔗 https://github.com/goldbergyoni/nodejs-testing-best-practices - Advanced Node.js testing practices and patterns --- ## Unit Testing ### Vitest (Modern Jest Alternative - Recommended for 2025) **⭐ vitest-dev/vitest** (12,000+ stars) ⚡ TRENDING - ⚡️ Next generation testing framework powered by Vite - 🔗 https://github.com/vitest-dev/vitest - **Use Case:** Modern, blazing-fast unit testing framework with native ESM, TypeScript, and JSX support - **Why Vitest in 2025:** - Built on Vite for lightning-fast test execution - Drop-in replacement for Jest with compatible API - Native ES modules, TypeScript, and JSX support out of the box - No separate build pipeline configuration needed - Parallel test execution by default - Released v3 in January 2025 with powerful CLI features - **When to Choose:** New projects, Vite-based apps, modern TypeScript/ESM codebases - **Comparison:** https://vitest.dev/guide/comparisons ### Jest (Industry Standard) **⭐ jestjs/jest** (44,000+ stars) - Delightful JavaScript Testing Framework with a focus on simplicity - 🔗 https://github.com/jestjs/jest - **Use Case:** Mature, widely-adopted testing framework with extensive ecosystem - **Why Jest:** - 40+ million weekly npm downloads - Rich feature set with built-in mocking, code coverage, and snapshot testing - Massive ecosystem and community support - Better support for React Native and legacy projects - Parallel test execution and built-in watch mode - **When to Choose:** React Native projects, legacy codebases, teams already using Jest - **Recommendation:** Use Vitest for new projects unless your framework/library has better Jest support --- ## Integration Testing **⭐ testdouble/testdouble.js** (1,500+ stars) - A minimal test double library for TDD with JavaScript - 🔗 https://github.com/testdouble/testdouble.js - **Use Case:** Sophisticated mocking and stubbing for integration tests **⭐ sinonjs/sinon** (9,600+ stars) - Test spies, stubs and mocks for JavaScript - 🔗 https://github.com/sinonjs/sinon - **Use Case:** Comprehensive mocking library for integration testing - **Features:** Spies, stubs, mocks, fake timers, fake XMLHttpRequest --- ## E2E Testing ### Playwright (Recommended for 2025) **⭐ microsoft/playwright** (65,000+ stars) ⚡ TRENDING - Playwright is a framework for Web Testing and Automation - 🔗 https://github.com/microsoft/playwright - **Use Case:** Modern, powerful E2E testing across all major browsers - **Why Playwright in 2025:** - Native support for Chrome, Firefox, and Safari (WebKit) - Multi-language support (JavaScript, TypeScript, Python, C#, Java) - Built-in parallel execution for fast test suites - Advanced network interception and API mocking - Seamless cross-origin testing - Mobile device emulation - Auto-wait and retry mechanisms for flake-free tests - Screenshot and video capture on failures - **When to Choose:** Cross-browser testing, large-scale projects, need for speed and stability - **Best Practices:** - Use data-test attributes for selectors - Mock API requests for deterministic tests - Keep tests independent - Integrate into CI/CD (GitHub Actions, GitLab CI) - Run essential tests for quick feedback, full suites on schedule ### Cypress (Alternative for SPA-focused Testing) **⭐ cypress-io/cypress** (46,000+ stars) - Fast, easy and reliable testing for anything that runs in a browser - 🔗 https://github.com/cypress-io/cypress - **Use Case:** Developer-friendly E2E testing with excellent DX - **Why Cypress:** - Runs directly in browser for native DOM access - Superior debugging experience with time-travel - Real-time reloads and interactive test runner - Powerful dashboard for visualizing test runs - Excellent for Single-Page Applications (SPAs) - **Limitations:** - JavaScript/TypeScript only - Chromium and Firefox only (no Safari) - Requires paid plan for parallel execution - Same-origin policy limitations - **When to Choose:** SPA-focused projects, teams prioritizing DX, fast setup requirements ### Comparison: Playwright vs Cypress | Feature | Playwright | Cypress | |---------|-----------|---------| | **Browser Support** | Chrome, Firefox, Safari | Chrome, Firefox only | | **Languages** | JS, TS, Python, C#, Java | JS, TS only | | **Parallel Execution** | Native & free | Paid plan required | | **Cross-Origin** | Seamless | Limited | | **Speed** | Faster for large suites | Fast for SPAs | | **DX** | Automation-focused | Developer-focused | --- ## React Testing **⭐ testing-library/react-testing-library** (19,000+ stars) ⚡ ESSENTIAL - 🐐 Simple and complete React DOM testing utilities that encourage good testing practices - 🔗 https://github.com/testing-library/react-testing-library - **Use Case:** Industry standard for testing React components (72% developer adoption in 2025) - **Philosophy:** "The more your tests resemble the way your software is used, the more confidence they can give you" - **Key Principles:** - Test behavior, not implementation details - Query components as users would (by text, role, label) - Avoid testing internal component state - Promote accessibility-friendly selectors - **Best Practices:** - Use `screen` queries for better error messages - Prefer `getByRole` and `getByLabelText` queries - Use `userEvent` over `fireEvent` for realistic interactions - Test user workflows, not isolated components - **Works With:** Jest, Vitest, and any test runner **⭐ testing-library/react-hooks-testing-library** (5,277 stars) - 🐏 Simple and complete React hooks testing utilities - 🔗 https://github.com/testing-library/react-hooks-testing-library - **Use Case:** Testing React hooks in isolation - **Note:** Now integrated into React Testing Library for React 18+ **⭐ testing-library/user-event** (2,100+ stars) - Simulate user interactions for Testing Library - 🔗 https://github.com/testing-library/user-event - **Use Case:** More realistic user interaction simulation than fireEvent - **Features:** Keyboard navigation, click sequences, clipboard operations --- ## Testing Strategies & TDD ### Core Testing Principles (2025) 1. **Arrange-Act-Assert (AAA) Pattern** - Arrange: Set up test data and conditions - Act: Execute the code being tested - Assert: Verify the expected outcome - Benefits: Clear structure, easy debugging, consistent format 2. **Test Behavior, Not Implementation** - Focus on what code does, not how it works - Makes tests resilient to refactoring - Tests serve as effective documentation - Use descriptive test names that explain expected behavior 3. **Keep Tests Simple and Readable** - Short, flat, and delightful to work with - One assertion concept per test - Avoid complex setup with beforeEach/beforeAll - Use descriptive names for test scenarios 4. **Test Independence** - Each test should set up its own state - No dependencies between tests - Tests should pass in any order - Prevents flaky test results 5. **Avoid Overusing Mocks** - Mock only external dependencies - Prefer real implementations when possible - Too many mocks = testing mock behavior - Balance between isolation and realism ### The Testing Pyramid ``` /\ /E2E\ Small number (10-20%) /------\ /INTEGR.\ Moderate number (20-30%) /----------\ / UNIT \ Large number (50-70%) /--------------\ ``` **Target Coverage:** 70-80% overall (industry benchmark 2025) ### TDD Cycle (Red-Green-Refactor) 1. **Red:** Write a failing test first 2. **Green:** Write minimal code to pass the test 3. **Refactor:** Clean up code without changing behavior **Benefits:** - Reduces bugs by up to 40% - Identifies issues early in development - Improves code design and testability - Living documentation through tests ### Modern Testing Stack (2025) **Recommended Stack:** - **Unit Tests:** Vitest (or Jest for legacy projects) - **React Components:** React Testing Library + Vitest - **E2E Tests:** Playwright (or Cypress for SPAs) - **API Tests:** Vitest with MSW (Mock Service Worker) - **CI/CD:** GitHub Actions, GitLab CI, or Jenkins **Emerging Trends:** - AI-powered test generation and maintenance - Unified frameworks blending unit/integration/E2E - Visual and behavioral regression testing - Component testing in real browsers (Vitest Browser Mode, Playwright Component Tests) --- ## Additional Testing Tools **⭐ mochajs/mocha** (22,836 stars) - ☕️ Simple, flexible, fun JavaScript test framework - 🔗 https://github.com/mochajs/mocha - **Use Case:** Flexible testing framework with simple setup - **Note:** Consider Vitest or Jest for new projects **⭐ avajs/ava** (20,700+ stars) - Node.js test runner that lets you develop with confidence - 🔗 https://github.com/avajs/ava - **Use Case:** Minimal and fast Node.js test runner with isolated test processes **⭐ mswjs/msw** (15,000+ stars) - Seamless REST/GraphQL API mocking library for browser and Node.js - 🔗 https://github.com/mswjs/msw - **Use Case:** Mock APIs at network level for realistic testing - **Why MSW:** Works in both tests and browser, no code changes needed --- *Part of octocode-mcp resources collection*