Loads polyfills from https://polyfill.io/ before running tests.
Install the plugin with
npm install karma-polyfill --save-dev
Configure Karma to load the plugin as a framework and specify the features you need polyfilled:
The above configuration will load the https://cdn.polyfill.io/v2/polyfill.min.js?features=Promise,fetch script before your tests run.
Note that if you've included a
plugins section in your Karma config, you will need to add a
karma-polyfill entry to your plugins array.