JavaScript codecoverage tool for Grunt

npm install grunt-istanbul
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JavaScript codecoverage tool for Grunt

Getting Started

This plugin requires Grunt ~0.4.1

Install this grunt plugin next to your project's Gruntfile.js with: npm install grunt-istanbul

Then add this line to your project's Gruntfile.js gruntfile:



To use this grunt-istanbul plugin, register a grunt task to run the following:

  1. Instrument your source code
  2. Run your test suite against your instrumented source code
  3. Store your coverage results
  4. Make the report

For step 2, an environment variable can be used to determine which path to use for loading the source code to run the tests against. For example, when you normally run your tests you want them to point directly at your source code. But when you run your instanbul code coverage task you want your tests to point at your instrumented source code. The grunt-env plugin can be used for setting an environment variable in a grunt task. Here's an example solution that solves this problem using grunt-env and grunt-mocha-test:

// in Gruntfile.js
module.exports = function (grunt) {

    env: {
      coverage: {
        APP_DIR_FOR_CODE_COVERAGE: '../test/coverage/instrument/app/'
    instrument: {
      files: 'app/*.js',
      options: {
        lazy: true,
        basePath: 'test/coverage/instrument/'
    mochaTest: {
      options: {
        reporter: 'spec'
      src: ['test/*.js']
    storeCoverage: {
      options: {
        dir: 'test/coverage/reports'
    makeReport: {
      src: 'test/coverage/reports/**/*.json',
      options: {
        type: 'lcov',
        dir: 'test/coverage/reports',
        print: 'detail'

  grunt.registerTask('coverage', ['env:coverage', 'instrument', 'mochaTest',
    'storeCoverage', 'makeReport']);

// require_helper.js
module.exports = function (path) {
  return require((process.env.APP_DIR_FOR_CODE_COVERAGE || '../app/') + path);

// using requireHelper in a test
var requireHelper = require('../require_helper');
var formValidator = requireHelper('form_validator');

Also, checkout the example Gruntfile.js in this repo (note that you do not need to implement the reloadTasks task in this example): Gruntfile.js

more examples


In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using grunt.

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Copyright (c) 2014 taichi Licensed under the MIT license.

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