This is a fork of karma-parcel, which is not actively maintained anymore.

Use parcel to preprocess karma tests

To get all the needed packages:

npm i karma parcel-bundler karma-parcel -D

Add parcel to the frameworks to be used and to the files that should be preprocessed with it:

module.exports = function (config) {
  config.set({
    frameworks: ["mocha", "parcel"],

    // add patterns with all your tests even if they should not
    // be handled by parcel
    files: [
      "tests/**/*.js",
      {
        // parcel tests should not be watched. Parcel will do the
        // watching instead
        pattern: "parcel/**/*.js",
        watched: false,
        included: false
      }
    ],

    // let karma know which of the test files should be bundled
    // with parcel
    preprocessors: {
      "parcel/*": ["parcel"]
    }
  });
};

Some more parcel specific configuration can be passed to the underlying parcel instance via the parcelConfig attribute of your karma configuration:

module.exports = function (config) {
  config.set({
    // lot of karma configuration
    parcelConfig: {
      cacheDir: "/path/to/cache", // default: "./.cache"
      detailedReport: true, // default: false,
      logLevel: 2, // default: 1
      watch: true // default: config.autoWatch or false
    }
  });
};

The reason that watch can be set separate from config.autoWatch is so that parcel can rebuild changed files even if a karma run is triggered manually (e.g. from IntelliJ IDEA).

Parcel will create one bundle with all the files that are preprocessed with the parcel preprocessor. The preprocessor will emit an empty file instead of the actual content. The plugin will register a bundle file to karma's fileList with serve: false in order not to be handled by karma's middleware. To serve the bundled file, parcel's own middleware is registered and used

This plugin is heavily inspired by karma-browserify and karma-webpack.