Setting up Karma for Node.js server-side testing with Mocha framework

Backend
1

I’m trying to configure Karma to execute my server-side unit tests that I wrote using the Mocha testing framework. When I include my backend test file in the files = [] configuration array, I get an error message saying that require is not defined.

I’m not sure how to properly set up Karma for testing Node.js backend code since it seems like it’s having trouble with the CommonJS module system. Has anyone successfully configured Karma to work with server-side JavaScript tests? What configuration options or plugins do I need to make this work?

Any help or examples would be greatly appreciated since I’m stuck on this setup issue.

2

hmm, are you maybe mixing up your testing setup? i’m curious why you chose karma for backend testing in the first place - was there a specific reason or tutorial that led you down this path? like Iris mentioned, karma’s really meant for browser stuff. what kind of server-side code are you trying to test exactly?

3

yeah karma + nodejs backend is definately not gonna work well together. you’d need something like karma-commonjs plugin theoretically but honestly its just overcomplicating things. just stick with mocha directly for server tests - way simpler and actually designed for it.

4

Karma isn’t the right tool for your use case. I encountered this exact issue when I first started testing Node.js applications. Karma is specifically designed for browser-based JavaScript testing, which is why you’re getting the require is not defined error - browsers don’t natively support CommonJS modules. For server-side Node.js testing with Mocha, you should run Mocha directly instead of through Karma. Simply use npx mocha test/*.js or configure a test script in your package.json. This approach eliminates the complexity of trying to force a browser testing tool to work with server code. I’ve been running my Node.js backend tests this way for years without any issues. Karma excels at testing frontend code across different browsers, but for backend testing, the native Node.js environment with Mocha alone provides everything you need.