When you start building applications in Node.js, it is tempting to dive straight into writing features and only test them manually. While this can work for small projects, it quickly becomes a problem as your codebase grows. Bugs appear, existing features break when you add new ones, and manual testing becomes slow.
This is where test-driven development, or TDD, comes into play. TDD is a practice where you first write a test for a feature, watch it fail, then write the code to make it pass, and finally clean up your implementation while keeping the test green. This cycle encourages you to think clearly about what your code should do before you even write it.
In this article, we will walk through setting up a Node.js project for TDD, writing the first tests, and building a simple API with Jest and Supertest. By the end you will have a practical workflow that you can apply to your own projects.