JavaScript Lesson 33 | Testing Fundamentals | Vitest, Unit Tests, describe, it & expect

#javascript #testing #vitest Lesson 33: JavaScript Testing Fundamentals. Learn why testing matters and how to write real unit tests in JavaScript using Vitest. This lesson covers setting up a project with npm, installing Vitest as a dev dependency, configuring the test script, writing test files, and understanding the core testing functions describe(), it(), and expect(). In this lesson, I covered: • Why testing is important in JavaScript • How to initialize a project with npm init -y • How to add "type": "module" in package.json • Installing Vitest with --save-dev • Adding a custom test script • Exporting functions for testing • Writing test files with script.test.js • Using describe(), it(), and expect() • Testing functions like add(), isEven(), and capitalize() • Watching tests fail and pass in real time • Testing edge cases and common behaviors This lesson is a practical introduction to unit testing in JavaScript and helps you build confidence, catch bugs early, and write more reliable code.