old_contents: var webpack = require('webpack');
  
  module.exports = function (config) {
    config.set({
      browsers: [ process.env.CONTINUOUS_INTEGRATION ? 'Firefox' : 'Chrome' ], // use Firefox for Travis CI
      singleRun: true,
      frameworks: [ 'mocha' ],
      files: [
        'tests.webpack.js'
      ],
      preprocessors: {
        'tests.webpack.js': [ 'webpack', 'sourcemap' ]
      },
      reporters: [ 'dots' ],
      webpack: {
        devtool: 'inline-source-map',
        module: {
          loaders: [
            {
              test: /.jsx?$/,
              loader: 'babel-loader',
              exclude: /node_modules/,
              query: {
                presets: ['es2015', 'react']
              }
            }
          ]
        }
      },
      webpackServer: {
        noInfo: true
      }
    });
  };
  
new_contents: var webpack = require('webpack');
  
  module.exports = function (config) {
    config.set({
      browsers: [ process.env.CONTINUOUS_INTEGRATION ? 'Firefox' : 'Chrome' ], // use Firefox for Travis CI
      singleRun: true,
      frameworks: [ 'mocha' ],
      files: [
        'tests.webpack.js'
      ],
      preprocessors: {
        'tests.webpack.js': [ 'webpack', 'sourcemap' ]
      },
      reporters: [ 'dots' ],
      webpack: {
        devtool: 'inline-source-map',
        module: {
          loaders: [
            {
              test: /.jsx?$/,
              loader: 'babel-loader',
              exclude: /node_modules/,
              query: {
                presets: ['es2015', 'react']
              }
            },
            {
              test: /\.scss$/,
              loaders: ["style", "css?sourceMap", "sass?sourceMap"]
            },
          ]
        }
      },
      webpackServer: {
        noInfo: true
      }
    });
  };
  
subject: add sass-loader to karma config file