karma.conf.js

// Karma configuration
module.exports = function ( config ) {

    config.set( {

        // enable / disable watching file and executing tests whenever any file changes
        autoWatch: true,

        // base path that will be used to resolve all patterns (eg. files, exclude)
        basePath: '',

        // Uncomment if you want only certain browsers
        // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
        // browsers: [
        //     'ChromeHeadless',
        //     'Firefox',
        //     'Safari'
        // ],

        // enable / disable colors in the output (reporters and logs)
        colors: true,

        // Concurrency level
        // how many browser should be started simultaneous
        concurrency: Infinity,

        // https://github.com/litixsoft/karma-detect-browsers
        detectBrowsers: {

            // Enable/disable, default is true
            enabled: true,

            // Enable/disable phantomjs support, default is true
            usePhantomJS: false,

            // Use headless mode, for browsers that support it, default is false
            preferHeadless: true,

            // Post processing of browsers list where you can edit the list of browsers used by karma
            postDetection: function ( availableBrowsers ) {

                var result = availableBrowsers;

                // Remove SafariTechPreview
                result = availableBrowsers.filter( (browser) => browser !== 'SafariTechPreview');

                return result;

            }
        },

        // list of files / patterns to exclude
        exclude: [],

        // list of files / patterns to load in the browser
        files: [
            {
                watched: false,
                pattern: 'test/lib/viewport-size.js'
            },
            'src/viewport.js',
            // 'dist/viewport.min.js',
            'test/api-browser.js'

        ],

        // frameworks to use
        // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
        frameworks: [
            'chai',
            'mocha',
            'detectBrowsers'
        ],

        // level of logging
        // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
        logLevel: config.LOG_INFO,

        // web server port
        port: 9876,

        // preprocess matching files before serving them to the browser
        // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
        preprocessors: {
            // 'src/viewport.js': [ 'coverage' ]
        },

        plugins: [
            'karma-chai',
            'karma-mocha',
            'karma-chrome-launcher',
            'karma-edge-launcher',
            'karma-firefox-launcher',
            'karma-ie-launcher',
            'karma-safari-launcher',
            'karma-safaritechpreview-launcher',
            'karma-opera-launcher',
            'karma-detect-browsers'
        ],

        // test results reporter to use
        // possible values: 'dots', 'progress'
        // available reporters: https://npmjs.org/browse/keyword/karma-reporter
        reporters: [
            // 'coverage',
            'progress'
        ],

        // Continuous Integration mode
        // if true, Karma captures browsers, runs the tests and exits
        singleRun: false

    } );

};