karma-polyfill

Loads polyfills from https://polyfill.io/ before running tests.

Use

Install the plugin with npm:

npm install karma-polyfill --save-dev

Configure Karma to load the plugin as a framework and specify the features you need polyfilled:

 module.exports = function(config) {
  config.set({
    frameworks: ['polyfill'],
    polyfill: ['Promise', 'fetch'] // etc.
    // additional settings here ...
  });
};

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.