Almost config-free Istanbul code coverage reporter for Mocha usage in Grunt

grunt mocha istanbul task

Mocha reporter to generate coverage report of istanbul instrumented code, for grunt This doesn't force you to use PhantomJS, or instrument code for server or client-side.


  1. Install it using npm install grunt-mocha-istanbul --save-dev
  2. It needs mocha, grunt and istanbul to be installed locally on your project (aka, having them in your devDependencies)
  3. Call inside Gruntfile.js grunt.loadNpmTasks('grunt-mocha-istanbul')

Changes from 1.x

Since Istanbul has 2 versions (ES5 and ES6/harmony), it's up to you to install the desired version of Istanbul, it's now defined as a a peer dependency.

Introduced new task istanbul_check_coverage to enable coverage checking on more than one test run. See below for example.

Changes from 0.2.0

  • mocha_istanbul_check was removed and became part of the options under the check object


Most of the options that you pass to mocha is available in options:

module.exports = function(grunt){
        mocha_istanbul: {
            coverage: {
                src: 'test', // a folder works nicely 
                options: {
                    mask: '*.spec.js'
            coverageSpecial: {
                src: ['testSpecial/*/*.js', 'testUnique/*/*.js'], // specifying file patterns works as well 
                options: {
                    coverageFolder: 'coverageSpecial',
                    mask: '*.spec.js',
                    mochaOptions: ['--harmony','--async-only'], // any extra options 
                    istanbulOptions: ['--harmony','--handle-sigint']
            coveralls: {
                src: ['test', 'testSpecial', 'testUnique'], // multiple folders also works 
                options: {
                    coverage:true, // this will make the grunt.event.on('coverage') event listener to be triggered 
                    check: {
                        lines: 75,
                        statements: 75
                    root: './lib', // define where the cover task should consider the root of libraries that are covered by tests 
                    reportFormats: ['cobertura','lcovonly']
        istanbul_check_coverage: {
          default: {
            options: {
              coverageFolder: 'coverage*', // will check both coverage folders and merge the coverage results 
              check: {
                lines: 80,
                statements: 80
    grunt.event.on('coverage', function(lcovFileContentsdone){
        // Check below on the section "The coverage event" 
    grunt.registerTask('coveralls', ['mocha_istanbul:coveralls']);
    grunt.registerTask('coverage', ['mocha_istanbul:coverage']);

If there's a mocha.opts file inside the first src folder or file defined, it will warn if you are overwriting any options.

Coverage is written to coverage folder by default, in the same level as the Gruntfile.js

The check will fail the build if the thresholds are not met. It's a great possibility for CI-builds.


Mochas parameters, check []

An array of strings, any additional mocha parameters, manually set. Eg.: ['--harmony']

An array of strings, any additional istanbul parameters, manually set. Eg.: ['--harmony', '--handle-sigint']

Allows to override the default istanbul path to use another coverage library, such as ibrik. Need to set the full path to the bin (script that accepts stdin arguments) and is compatible with cover.

Setting this to true makes the task emit a grunt event coverage, that will contain the lcov data from the file, containing the following callback function(lcovcontent, done), and you must manually call done() when you are finished, else the grunt task will HANG, and won't allow any other tasks to finish. See more information below

Spits out the command line that would be called, just to make sure everything is alright

Setting this exclude files from coverage report, check istanbul help cover. You may use glob matching in here.

The mask for the tests to be ran. By default, mocha will execute the test folder and all test files. Will override any files specified in src and instead use the mask on those files' folders.

Suppresses the output from Mocha and Istanbul

Name of the output of the coverage folder

Name of report formats. You can specify more than one. If you intend to use the coverage option to true or do any checks, you must add: ['yourformat','lcovonly'], since it's needed for the file to be created.

Supported formats:

    html - produces a bunch of HTML files with annotated source code
    lcovonly - produces an file
    lcov - produces html + lcov files. This is the default format
    cobertura - produces a cobertura-coverage.xml file for easy Hudson integration
    text-summary - produces a compact text summary of coverage, typically to console
    text - produces a detailed text table with coverage for all files
    teamcity - produces service messages to report code coverage to TeamCity

The root path to look for files to instrument, defaults to .. Can help to exclude directories that are not part of the code whose coverage should be checked.

The type of report to print to console. Can be one of 'summary', 'detail', 'both', or 'none'. By default, Istanbul will print the 'summary' report.

Number of statements threshold to consider the coverage valid

Number of lines threshold to consider the coverage valid

Number of branches threshold to consider the coverage valid

Number of functions threshold to consider the coverage valid

The coverage event

When you set the option coverage to true, you'll receive the coverage/ file contents:

grunt.event.on('coverage', function(lcovdone){
    done(); // or done(false); in case of error 

This is mainly useful so you can send it to, for example, coveralls (using coveralls):

grunt.event.on('coverage', function(lcovdone){
    require('coveralls').handleInput(lcov, function(err){
        if (err) {
            return done(err);

This way, Travis-CI can send the Istanbul generated LCOV directly to website in this example, but you could create any transform for Jenkins, TeamCity, Hudson, etc.