Generate code coverage using Istanbul.

The easiest way is to keep karma-coverage as a devDependency in your package.json.

{
  "devDependencies": {
    "karma": "~0.10",
    "karma-coverage": "~0.1"
  }
}

You can simple do it by:

npm install karma-coverage --save-dev

Following code shows the default configuration...

// karma.conf.js
module.exports = function(config) {
  config.set({
    files: [
      'src/**/*.js',
      'test/**/*.js'
    ],

    // coverage reporter generates the coverage
    reporters: ['progress', 'coverage'],

    preprocessors: {
      // source files, that you wanna generate coverage for
      // do not include tests or libraries
      // (these files will be instrumented by Istanbul)
      'src/*.js': ['coverage']
    },

    // optionally, configure the reporter
    coverageReporter: {
      type : 'html',
      dir : 'coverage/'
    }
  });
};

Type: String

Possible Values:

• html (default)
• lcov (lcov and html)
• lcovonly
• text
• text-summary
• cobertura (xml format supported by Jenkins)

If you set type to text or text-summary, you may set the file option, like this.

coverageReporter = {
  type : 'text',
  dir : 'coverage/',
  file : 'coverage.txt'
}

If no filename is given, it will write the output to the console.

Type: String

Description: This will be used to output coverage reports. When you set a relative path, the directory is resolved against the basePath.

For more information on Karma see the homepage.