old_contents: 
  var postcssImport = require('postcss-import')
  var postcssCustomMedia = require('postcss-custom-media')
  var postcssCustomProperties = require('postcss-custom-properties')
  var postcssCalc = require('postcss-calc')
  
  module.exports = function (config) {
    config.set({
      browsers: [
        'Firefox'
      ],
  
      files: [
        './test/index.js'
      ],
  
      frameworks: [ 'chai', 'mocha' ],
  
      plugins: [
        'karma-chrome-launcher',
        'karma-firefox-launcher',
        'karma-safari-launcher',
        'karma-chai',
        'karma-mocha',
        'karma-mocha-reporter',
        'karma-webpack'
      ],
  
      preprocessors: {
        './test/index.js': [ 'webpack' ]
      },
  
      reporters: [ 'mocha' ],
      singleRun: true,
  
      webpack: {
        module: {
          loaders: [
            {
              test: /\.jsx?$/,
              exclude: /node_modules/,
              loader: 'babel-loader'
            },
            {
              test: /\.css$/,
              loader: 'style-loader!css-loader!postcss-loader'
            },
            {
              test: /\.json$/,
              loader: 'json-loader'
            }
          ]
        },
        postcss: function () {
          return [
            postcssImport,
            postcssCustomMedia,
            postcssCustomProperties,
            postcssCalc
          ]
        }
      },
  
  
      webpackMiddleware: {
        noInfo: true
      },
  
      client: {
        mocha: {
          reporter: 'html',
          ui: 'bdd'
        }
      }
  
    })
  }
  
  
new_contents: 
  var postcssImport = require('postcss-import')
  var postcssCustomMedia = require('postcss-custom-media')
  var postcssCustomProperties = require('postcss-custom-properties')
  var postcssCalc = require('postcss-calc')
  
  module.exports = function (config) {
    config.set({
      browsers: [
        'Firefox'
      ],
  
      files: [
        './test/index.js'
      ],
  
      frameworks: [ 'chai', 'mocha' ],
  
      plugins: [
        'karma-firefox-launcher',
        'karma-chai',
        'karma-mocha',
        'karma-mocha-reporter',
        'karma-webpack'
      ],
  
      preprocessors: {
        './test/index.js': [ 'webpack' ]
      },
  
      reporters: [ 'mocha' ],
      singleRun: true,
  
      webpack: {
        module: {
          loaders: [
            {
              test: /\.jsx?$/,
              exclude: /node_modules/,
              loader: 'babel-loader'
            },
            {
              test: /\.css$/,
              loader: 'style-loader!css-loader!postcss-loader'
            },
            {
              test: /\.json$/,
              loader: 'json-loader'
            }
          ]
        },
        postcss: function () {
          return [
            postcssImport,
            postcssCustomMedia,
            postcssCustomProperties,
            postcssCalc
          ]
        }
      },
  
  
      webpackMiddleware: {
        noInfo: true
      },
  
      client: {
        mocha: {
          reporter: 'html',
          ui: 'bdd'
        }
      }
  
    })
  }
  
  
subject: Adjust karma config