IntelliJ IDEA 2017.3 Help

Jest

This feature is only supported in the Ultimate edition.

Jest is a testing platform for client-side JavaScript applications and React applications specifically. Learn more about the platform from Jest Official website.

You can run and debug tests with Jest right in IntelliJ IDEA. You can see the test results in a treeview and easily navigate to the test source from there. Test status is shown next to the test in the editor with an option to quickly run it or debug it.

Before you start

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

Installing Jest

Open the built-in IntelliJ IDEA Terminal (Alt+F12) and type npm install --save-dev jest at the command prompt.
See also Getting Started on the Jest official website.

Running tests

With IntelliJ IDEA, you can quickly run a single Jest 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 run.png or rerun.png 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 ws_icon_test_status.png in the left gutter.

To create a Jest run configuration

  1. Open the Run/Debug Configuration dialog box (Run | Edit Configurations on the main menu).
  2. Click new on the toolbar and select Jest from the list. The Run/Debug Configuration: Jest dialog box opens.
  3. Specify the Node interpreter to use and the location of the jest, react-scripts, react-script-ts, react-super-scripts, or react-awesome-scripts package.
  4. Specify the working directory of the application.

    By default, the Working directory field shows the project root folder. To change this predefined setting, specify the path to the desired folder or choose a previously used folder from the list.

  5. Optionally specify the jest.config file to use: choose the relevant file from the drop-down list, or click browseButton and choose it in the dialog that opens, or just type the path in the text box. If the field is empty, IntelliJ IDEA looks for a package.json file with a jest key. The search is performed in the file system upwards from the working directory. If no appropriate package.json file is found, then the Jest default configuration is used.
  6. Optionally configure rerunning the tests automatically on changes in the related source files. To do that, add the --watch flag in the Jest options field.

To run tests via a run configuration

  1. Select the Jest run/debug configuration from the list on the main toolbar and click run to the right of the list.
  2. The test server starts automatically without any steps from your side. View and analyze messages from the test server in 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.

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

Snapshot testing

IntelliJ IDEA integration with Jest supports such a great feature as snapshot testing. If a snapshot does not match the rendered application the test fails. This indicates that either some changes in your code have caused this mismatch or the snapshot is outdated and needs to be updated. To update the snapshot for a failed test, use the Click to update snapshot link in the Test Runner tab of the Run tool window:

ws_jest_update_snapshot.png

Debugging tests

With IntelliJ IDEA, you can quickly start debugging a single Jest 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 run.png or rerun.png 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 Jest run/debug configuration as described above.
  2. Select the Jest run/debug configuration from the list on the main toolbar and click debug 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 Jest tests. IntelliJ IDEA displays this statistics in a dedicated tool window and marks covered and uncovered lines visually right in the editor.

To run tests with coverage

  1. Create a Jest run/debug configuration as described above.
  2. Select the Jest run/debug configuration from the list on the main toolbar and click runWithCoverage to the right of the list.
    Alternatively, quickly run a specific suite or a test with coverage from the editor: click run.png or rerun.png in the left gutter and choose Run <test_name> with Coverage from the pop-up list.
  3. Monitor the code coverage in the Coverage tool window. The report shows how many files were covered with tests and the percentage of covered lines in them. From the report you can jump to the file and see what lines were covered – marked green – and what lines were not covered – marked red:
    ws_jest_coverage_report.png

Last modified: 12 December 2017

See Also