There are currently two main module formats in the JavaScript ecosystem: ECMAScript Modules (ESM) and CommonJS (CJS). CJS was first, but ESM is now the JavaScript standard and is the future. The main difference between the two is how they import files.
There are tons of options for test packages and frameworks within the JavaScript ecosystem, both on the backend and frontend. This is my knowledge dump of them.
Disclaimer: This is only what I know about each package from browsing its docs, my experiences with them, and my, often strong (beware), opinions. I can't possibly hear or know about all available testing packages.