Unit testing is a very important aspect of software development. It involves testing the smallest units of code (eg. functions or methods) and if written well, they act as a guard rail whenever your code violates its expected behavior. In this article, we'll cover all the steps required to write unit tests for your node express API. We'll be using mocha(https://mochajs.org/) and chai (https://www.chaijs.com/) for our API. The API only provides five endpoints: 'GET /health/sync' - returns 'OK' synchronously.