Jasmine is a Behavior Driven Development testing framework for JavaScript. It does not rely on browsers, DOM, or any JavaScript framework. Thus it’s suited for websites, Node.js projects, or anywhere that JavaScript can run.
Problem

Console error
http://localhost:9876/_karma_webpack_/main.js net::ERR_ABORTED 404 (Not Found)
Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "". Strict MIME type checking is enforced for module scripts per HTML spec.
Solution
Use the watch parameter for more information/errors.
npx ng test --watch