API testing is essential to ensure your endpoints behave as expected across all scenarios. In this guide, we’ll explore how to use Jest and Supertest to test a sample API with various response types, including success, authentication errors, and validation errors. By the end, you’ll understand how to apply these tools to check for different response structures and status codes. 0. Prerequisites: Setting Up Your Environment Before diving into API testing, it’s important to ensure that your development environment is properly set up. Here’s what you need to do: Step 1: Install Node.js and npm Node.js is a JavaScript runtime that allows you to run JavaScript code on the server side. It comes with npm (Node Package Manager), which helps you install and manage packages. Installation Steps: Download and install Node.js from the official website . To verify the installation, open your terminal and run: node -v npm -v This should display the installed versions of Node.js...