Testing JavaScript with Karma

Before you start

1. Make sure the Node.js runtime environment is installed on your computer.
2. Install and enable the NodeJS and Karma repository plugins on the Plugins page as described in Installing, Updating and Uninstalling Repository Plugins and Enabling and Disabling Plugins.

Installing Karma and plugins

Open the built-in IntelliJ IDEA Terminal (press Alt+F12 or choose View | Tool Windows | Terminal on the main menu) and type one of the following commands at the command prompt:

• npm install if Karma and all the required plugins are already defined in package.json.
• To install Karma and the required plugins (e.g. karma-jasmine or jasmine-core) as development dependencies
  npm install --save-dev karma npm install --save-dev <required_karma_plugin> <another_required_karma_plugin>

Learn more on the Karma official website.

Generating a Karma configuration file

Karma tests are run according to a karma.conf.js configuration file which is generated in the interactive mode. If you already have karma.conf.js in your project, just skip this step. For more details on Karma configuration, see Karma official website.

To create a Karma configuration file

1. Open the Terminal and start the karma.conf.js generation wizard by typing one of the following depending on your operating system:
   • For macOS and Linux:
     ./node_modules/karma/bin/karma init
   • For Windows:
     npm install -g karma-cli
karma init
2. Answering the questions of the wizard, specify the testing framework to use and the browsers to be captured automatically. See also Karma Files: Pattern matching.

Running tests

With IntelliJ IDEA, you can quickly run a single Karma test right from the editor or create a run/debug configuration to execute some or all of your tests.

To run a single test from the editor
Click or in the left gutter and choose Run <test_name> from the pop-up list. You can also see whether a test has passed or failed right in the editor, thanks to the test status icons in the left gutter.

To create a Karma run configuration

1. Open the Run/Debug Configuration dialog box (Run | Edit Configurations on the main menu).
2. Click on the toolbar and select Karma from the list. The Run/Debug Configuration: Karma dialog box opens.
3. Specify the Node interpreter to use, the location of the karma package, and the path to karma.conf.js.

To run tests via a run configuration

1. Select the Karma run/debug configuration from the list on the main toolbar and click  to the right of the list.
2. The Karma test server starts automatically without any steps from your side. View and analyze messages from the test server in the Karma Server tab of the Run tool window.
3. Monitor test execution in the Test Runner tab of the Run tool window as described in Monitoring and Managing Tests.

Navigation

With IntelliJ IDEA, you can jump between a file and the related test file. Navigation from a test result in the Test Runner Tab to the test is also supported.

To jump between a file and the related test file
Open the file in the editor and choose Go To | Test or Go To | Test Subject on the context menu, or just press Ctrl+Shift+T.

To jump from a test result to the test
Select the test name in the Test Runner tab and choose Jump to Source on the context menu.

The test file opens in the editor with the cursor placed at the test definition.

Debugging tests

With IntelliJ IDEA, you can quickly start debugging a single Karma test right from the editor or create a run/debug configuration to debug some or all of your tests.

To start debugging a single test from the editor
Click or in the left gutter and choose Debug <test_name> from the pop-up list.

To launch test debugging via a run/debug configuration

1. Create a Karma run/debug configuration as described above.
2. Select the Karma run/debug configuration from the list on the main toolbar and click  to the right of the list.
3. In the Debug Tool Window that opens, proceed as usual: step through the tests, stop and resume test execution, examine the test when suspended, etc.

Monitoring code coverage

With IntelliJ IDEA, you can also monitor how much of your code is covered with Karma tests. IntelliJ IDEA displays this statistics in a dedicated tool window and marks covered and uncovered lines visually right in the editor. To monitor coverage, you need to install the karma-coverage package and update karma.conf.js.

To install karma-coverage
Open the built-in IntelliJ IDEA Terminal (press Alt+F12 or choose View | Tool Windows | Terminal on the main menu) and type npm install  --save-dev karma-coverage.

To add karma-coverage definition to the configuration file
Open karma.conf.js in the editor and add the following information to it:

1. Locate the reporters definition and add coverage to the list of values in the format:
   reporters: ['progress', 'coverage']
2. Add a preprocessors definition and specify the coverage scope in the format:
   preprocessors: {'**/*.js': ['coverage']}

To launch tests with coverage

1. Create a Karma run/debug configuration as described above.
2. Select the Karma run/debug configuration from the list on the main toolbar and click  to the right of the list. Alternatively, use the test icons in the editor to quickly run a specific suite or a test with coverage:

   

3. Monitor the code coverage in the Coverage tool window. Note that for Karma tests, the Coverage tool window does not show the Generate Coverage Report toolbar button because a coverage report is actually generated on the disk every time Karma tests are run. The format of a coverage report can be configured in the configuration file, for example:
   // karma.conf.js module.exports = function(config) { config.set({ ... // optionally, configure the reporter coverageReporter: { type : 'html', dir : 'coverage/' } ... });};
   The following type values are acceptable:
   • html produces a bunch of HTML files with annotated source code.
   • lcovonly produces an lcov.info file.
   • lcov produces HTML + .lcov files. This format is applied by default.
   • cobertura produces a cobertura-coverage.xml file for easy Hudson integration.
   • text-summary produces a compact text summary of coverage, typically to the console.
   • text produces a detailed text table with coverage for all files.