PyCharm 2024.2 Help

Jest

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

You can run and debug tests with Jest right in PyCharm. 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 you have Node.js on your computer.

  2. Make sure the JavaScript and TypeScript plugin is enabled in the settings. Press Ctrl+Alt+S to open settings and then select Plugins. Click the Installed tab. In the search field, type JavaScript and TypeScript. For more information about plugins, refer to Managing plugins.

Install and configure Jest

  • In the embedded Terminal (Alt+F12) , type:

    npm install --save-dev jest

Learn more from Getting Started and Configuring Jest on the Jest official website.

Run tests

With PyCharm, 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.

For more information about creating Vitest tests for JavaScript and TypeScript code, refer to Vitest features on the Vitest official website.

Run a single test from the editor

  • Click the Run icon or the Rerun icon in the gutter and select Run <test_name> from the list.

    Run single test from the editor

    You can also see whether a test has passed or failed right in the editor, thanks to the test status icons Test passed and Test failed in the gutter.

Run all tests in a folder from the Project tool window

  • In the Project tool window, select the folder with the tests, and then select Run 'Tests in <folder name>'.

    Run all tests in a folder

Create a Jest run configuration

  1. Open the Run/Debug Configuration dialog (Run | Edit Configurations in the main menu), click the Add button in the left-hand pane, and select Jest from the list. The Run/Debug Configuration: Jest dialog opens.

  2. Specify the Node.js interpreter to use.

    If you choose the Project alias, PyCharm will automatically use the project default interpreter from the Node interpreter field on the Node.js page . In most cases, PyCharm detects the project default interpreter and fills in the field itself.

    You can also choose another configured local or remote interpreter or click the Browse button and configure a new one.

  3. Specify 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.

  5. Specify the tests to run. This can be a specific test or suite, an entire test file, or a folder with test files.

  6. Optionally specify the jest.config.js or jest.config.ts file to use: select the relevant file from the list, or click the Browse button and select it in the dialog that opens, or just type the path in the field.

    If the field is empty, PyCharm 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 a Jest default configuration is generated on the fly.

  7. Optionally:

    Configure rerunning tests automatically on changes in the related source files. To do that, add the --watch flag in the Jest options field.

    You can also turn the watch mode on later by pressing the Watch for Changes toggle button in the Run tool window during a test session, refer to Rerun test automatically on changes (watch mode) below.

  8. Optionally:

    Specify the environment variables for executing commands. PyCharm will show these variables in completion lists for process.env.

    Completion for environment variables from Jest run configuration
  9. In the Node options field, optionally type the Node.js-specific command-line options to be passed to the Node.js executable file. The acceptable options are:

    • Use --require coffeescript/register to have CoffeeScript files compiled into JavaScript on the fly during run.

      This mode requires that the register.js file, which is a part of the coffeescript package, is located inside your project. Therefore, make sure you have the coffeescript package installed locally as described in Install the CoffeeScript compiler.

    • Use --inspect or --inspect-brk parameter for Chrome Debugging Protocol support.

    • To use ECMAScript Modules in your project, add the —experimental-vm-modules flag to the Node options field.

Run tests via a run configuration

  1. Select the Jest run/debug configuration from the list of configurations and click the Run icon   in the list or on the toolbar.

  2. Monitor test execution and analyze test results in the Test Runner tab of the Run tool window. For more information, refer to Explore test results.

Rerun failed tests

  • Click the Rerun Failed Tests icon on the test results toolbar. PyCharm will execute all the tests that failed during the previous session.

  • To rerun a specific failed test, select Run <test name> on its context menu.

For more information, refer to Rerunning tests.

Rerun tests automatically on changes (watch mode)

PyCharm supports the watch mode in which a test is rerun automatically as soon as any changes are made to the test-related source file. As a result, you can just make changes to your code without having to rerun tests manually or restart the Jest run/debug configuration.

Navigation

With PyCharm, you can jump between a file and the related test file or from a test result in the Test Runner Tab to the test.

With PyCharm, you can jump between a file and the related test file and between a test or suite definition and its result in the Test Runner Tab.

  • To jump between a test and its subject or vice versa, open the file in the editor and select Go to | Test or Go to | Test Subject from the context menu, or just press Ctrl+Shift+T.

  • To jump from a test result to the test definition, click the test name in the Test Runner tab twice, or select Jump to Source from the context menu, or just press F4. The test file opens in the editor with the caret placed at the test definition.

  • To jump from a test or suite definition to its result in the Test Runner tab, click the Test passed icon or the Test failed icon in the gutter and choose Select <test_name> in Test Tree from the list.

    Jump from test definition to the Test Tree
  • For failed tests, PyCharm brings you to the failure line in the test from the stack trace. If the exact line is not in the stack trace, you will be taken to the test definition.

    Jump to the failure line from a failed Jest test

Snapshot testing

PyCharm integration with Jest supports such a great feature as snapshot testing.

When you run a test with a .toMatchSnapshot() method, Jest creates a snapshot file in the __snapshots__ folder. To jump from a test to its related snapshot, click the Go to snapshot (camera) icon in the gutter next to the test or select the required snapshot from the context menu of the .toMatchSnapshot() method.

Jest snapshot testing: jump from a test file to the corresponding snapshot

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 see what caused this mismatch, open the PyCharm built-in Diff Viewer via the Click to see difference link in the right-hand pane of the Test Runner tab.

Jest snapshots: compare the expected and actual snapshots in the PyCharm Diff Viewer

You can update outdated snapshots right from the Test Runner tab of the Run tool window.

  • To update the snapshot for a specific test, use the Click to update snapshot link next to the test name.

  • To update all outdated snapshots for the tests from a file, use the Click to update failed snapshots next to the test filename.

Jest snapshot testing: update snapshots

Debug tests

With PyCharm, 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.

  • Set the breakpoints where necessary.

  • To start debugging a single test from the editor, click the Run button or the Rerun icon in the gutter and select Debug <test_name> from the list.

  • To start debugging all tests in a folder, select the folder in the Project tool window, and then select Debug 'Tests in <folder name>' from the context menu.

    Debug all tests in a folder
  • To launch test debugging via a run/debug configuration, create a Jest run/debug configuration as described above.

    Then select the Jest run/debug configuration from the list of configurations and click the Debug icon   in the list or on the toolbar.

In the Debug tool window that opens, proceed as usual: step through the tests, stop and resume test execution, examine the test when suspended, run JavaScript code snippets in the Console, and so on.

Monitor code coverage

With PyCharm, you can also monitor how much of your code is covered with Jest tests. PyCharm displays this statistics in a dedicated Coverage tool window and marks covered and uncovered lines visually in the editor and in the Project tool window.

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 Run with Coverage icon  to the right of the list.

    Alternatively, quickly run a specific suite or a test with coverage from the editor: click the Run button or the Rerun button in the gutter and select Run <test_name> with Coverage from the list.

    Run Jest tests with coverage from the editor
  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:

    Jest Coverage report

Run Jest tests with Node.js inside a Docker container

With PyCharm, you can run Jest tests inside a Docker container just in the same way as you do it locally.

Before you start

  1. Install the Node.js and Node.js Remote Interpreter plugins on the Settings | Plugins page, tab Marketplace, as described in Installing plugins from JetBrains Marketplace.

  2. Make sure the Docker plugin is enabled in the settings. Press Ctrl+Alt+S to open settings and then select Plugins. Click the Installed tab. In the search field, type Docker. For more information about plugins, refer to Managing plugins.

  3. Download, install, and configure Docker as described in Docker

  4. Configure a Node.js remote interpreter in Docker or via Docker Compose and set it as default in your project. Also make sure the package manager associated with this remote interpreter is set as project default.

  5. Open your package.json and make sure Jest is listed in the devDependencies section:

    { "name": "node-express", "version": "0.0.0", "private": true, "dependencies": { "cookie-parser": "~1.4.4", "debug": "~2.6.9", "express": "~4.16.1", "http-errors": "~1.6.3", "morgan": "~1.9.1", "pug": "^3.0.2" }, "devDependencies": { "eslint": "^8.1.0", "http-server": "^14.0.0", "jest": "^27.3.1" } }
  6. Right-click anywhere in the editor and select Run '<package manager> install' from the context menu.

Run tests

  1. Create tests according to the instructions from the Jest official website.

  2. Proceed as with local development: run and debug single tests right from the editor or create a run/debug configuration to launch some or all of your tests as described in Run tests and Debug tests above.

Last modified: 28 June 2024