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Karma can generate code coverage using awesome Istanbul. If you want to generate the coverage, you need to configure up to three parts:

  • preprocessor coverage (required)
  • reporter coverage (required)
  • reporter options (optional)

Preprocessor #

The preprocessor configures which files should be tested for coverage. For example if all your code lives in lib/ you need to add this to your configuration file.

preprocessors = {
  '**/lib/*.js': 'coverage'

You should not however include the files that aren't directly related to your program, e.g. libraries, mocks, neither tests.

This is a BAD example

files = [
preprocessors = {
  '**/*.js': 'coverage'

In this example also JASMINE and JASMINE_ADAPTER get included but they shouldn't as these file are only for the test setup used and not for your program.

If you include these files there can occur side effects like the following,

  • a part of the code coverage report will be output in the installation directory of Karma.
  • the code coverage rate is reduced unfairly.

Reporter #

To activate the coverage reporter add this to your configuration file.

reporters = ['coverage'];

This will create a coverage report for every browser that the tests are run in. In addition, it will create a JSON file that outputs the intermediate data.

Reporter Options #

The reporter defaults to the following values.

coverageReporter = {
  type : 'html',
  dir : 'coverage/'

If you want to configure it yourself here are the options explained.

type #

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.

dir #

Type: String

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