Jest

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It works with projects using: Babel, TypeScript, Node, React, Angular, Vue, and more.

When to Use

• React Apps: The default and most supported runner for Create React App / Next.js (historically).
• Snapshot Testing: When you want to ensure UI or JSON structures haven't changed unexpectedly.
• Legacy/Standard: Extensive community plugins and support.

Quick Start

// sum.js
function sum(a, b) {
  return a + b;
}
module.exports = sum;