Code coverage generated for wrong files

[sashafklein]

We've got an app based off the newest Webpack2 version of this starter. It's generally working great, but we're struggling getting code coverage to work. Specifically, as with this closed issue (#1299), coverage isn't reporting for our actual files, but seems to only spit out data about the Webpack config files -- karma.config.js, webpack.config.js and project.config.js, but nothing else!

Here's what we've tried so far:

package.json

    "test": "env NODE_ENV=test nyc --reporter=html node ./node_modules/karma/bin/karma start config/karma.config",

karma.config.js

const argv = require('yargs').argv;
const project = require('../project.config');
// const webpackConfig = require('../build/webpack.config');
const debug = require('debug')('app:config:karma');
const path = require('path');

debug('Creating configuration.');

const webpackConfig = require('../build/webpack.config');

const TEST_BUNDLER = './tests/test-bundler.js';

// Add istanbul instrumenter to webpack rules
webpackConfig.module.rules = webpackConfig.module.rules.concat(
  {
		// delays coverage til after tests are run, fixing transpiled source
		// coverage error
    enforce: 'post',
    test: /\.js$/,
    exclude: /(tests|node_modules|bower_components|build)\//,
    loader: 'istanbul-instrumenter-loader'
  }
);

const karmaConfig = {
  basePath: '../',
  browsers: ['ChromeHeadless'],
  singleRun: !argv.watch,
  coverageReporter: {
    reporters: [
      { type: 'text-summary' },
      'coverage-istanbul'
    ]
  },
  files: [{
    pattern: TEST_BUNDLER,
    watched: false,
    served: true,
    included: true
  }],
  frameworks: ['mocha'],
  preprocessors: {
    [TEST_BUNDLER]: ['webpack']
  },
  logLevel: 'WARN',
  browserConsoleLogOptions: {
    terminal: true,
    format: '%b %T: %m',
    level: ''
  },
  plugins: ['karma-mocha', 'karma-chrome-launcher', 'karma-webpack-with-fast-source-maps', 'karma-coverage-istanbul-reporter'],
  webpack: {
    entry: TEST_BUNDLER,
    devtool: 'cheap-module-source-map',
    module: webpackConfig.module,
    plugins: webpackConfig.plugins,
    resolve: Object.assign({}, webpackConfig.resolve, {
      alias: Object.assign({}, webpackConfig.resolve.alias, {
        sinon: 'sinon/pkg/sinon.js',
        support: path.resolve(project.basePath, 'tests/support/')
      })
    }),
    externals: {
      'react/addons': 'react',
      'react/lib/ExecutionEnvironment': 'react',
      'react/lib/ReactContext': 'react'
    }
  },
  webpackMiddleware: {
    stats: 'errors-only',
    noInfo: true
  },
  coverageIstanbulReporter: {

    // reports can be any that are listed here: https://github.com/istanbuljs/istanbul-reports/tree/590e6b0089f67b723a1fdf57bc7ccc080ff189d7/lib
    reports: ['html', 'text-summary'],

    // base output directory. If you include %browser% in the path it will be replaced with the karma browser name
    dir: path.join(__dirname, 'coverage'),

    // if using webpack and pre-loaders, work around webpack breaking the source path
    fixWebpackSourcePaths: true,

    // stop istanbul outputting messages like `File [${filename}] ignored, nothing could be mapped`
    skipFilesWithNoCoverage: true

    // Most reporters accept additional config options. You can pass these through the `report-config` option
    // 'report-config': {
    //   // all options available at: https://github.com/istanbuljs/istanbul-reports/blob/590e6b0089f67b723a1fdf57bc7ccc080ff189d7/lib/html/index.js#L135-L137
    // }
  }
};

module.exports = (cfg) => cfg.set(karmaConfig);

tests/test-bundler.js

/* eslint no-extend-native:0 */

// ---------------------------------------
// Test Environment Setup
// ---------------------------------------

import React from 'react';
import sinon from 'sinon';
import chai from 'chai';
import sinonChai from 'sinon-chai';
import chaiAsPromised from 'chai-as-promised';
import chaiEnzyme from 'chai-enzyme';
import { shallow } from 'enzyme';

chai.use(sinonChai);
chai.use(chaiAsPromised);
chai.use(chaiEnzyme());

global.chai = chai;
global.sinon = sinon;
global.expect = chai.expect;
global.should = chai.should();
global.assert = chai.assert;

global.mockComp = (Component, props = {}) => shallow(<Component { ...props } />);

// ---------------------------------------
// Require Tests
// ---------------------------------------
// for use with karma-webpack-with-fast-source-maps
const __karmaWebpackManifest__ = []; // eslint-disable-line
const inManifest = (path) => ~__karmaWebpackManifest__.indexOf(path);

// require all `tests/**/*.spec.js`
const testsContext = require.context('./', true, /\.spec\.js$/);

// only run tests that have changed after the first pass.
const testsToRun = testsContext.keys().filter(inManifest)
;(testsToRun.length ? testsToRun : testsContext.keys()).forEach(testsContext);

// require all `src/**/*.js` except for `main.js` (for isparta coverage reporting)
const componentsContext = require.context('../src/', true, /^((?!main|reducers).)*\.js$/);
componentsContext.keys().forEach(componentsContext);

It successfully creates an HTML file in coverage/index.html which reports the coverage, but again, only for those three config files, not for the actual tests running on our codebase.

Any ideas what we've got wrong here?

Thanks