After months of using Jest for unit testing, we decided to take the plunge and migrate to the built-in node:test runner. The results were surprising, with some features working seamlessly and others requiring significant rework. In this post, we'll share our journey and the lessons we learned along the way. Introduction to node:test The node:test runner is a built-in testing framework that comes with Node.js. It's designed to be fast, efficient, and easy to use. Here's an example of a simple test using node:test: import { test } from ' node:test ' ; import { Command } from ' @aws-sdk/client-lambda ' ; test ( ' Lambda client test ' , async ( t ) => { const lambdaClient = new Command (); const response = await lambdaClient (); t . equal . responseStatusCode , 200 ; }); Enter fullscreen mode Exit fullscreen mode Warning: When using node:test, make sure to handle errors properly, as unhandled errors can cause the test runner to crash.…