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How to Contribute

Code of Conduct

Jest has adopted the OpenJS Code of Conduct that we expect project participants to adhere to. See CODE_OF_CONDUCT.md.

Open Development

All work on Jest happens directly on GitHub. Both core team members and external contributors send pull requests which go through the same review process.

main is unsafe

We will do our best to keep main in good shape, with tests passing at all times. But in order to move fast, we will make API changes that your application might not be compatible with. We will do our best to communicate these changes and always version appropriately so you can lock into a specific version if need be.

Workflow and Pull Requests

Before submitting a pull request, please make sure the following is done…

  1. Fork the repo and create your branch from main. A guide on how to fork a repository: https://help.github.com/articles/fork-a-repo/

    Open terminal (e.g. Terminal, iTerm, Git Bash or Git Shell) and type:

    $ git clone https://github.com/<your_username>/jest
$ cd jest
$ git checkout -b my_branch

    Note: Replace <your_username> with your GitHub username

  2. Jest uses Yarn for running development scripts. If you haven't already done so, please run corepack enable.

  3. Make sure you have python installed. Python is required by node-gyp that is used when running yarn install.

    To check your version of Python and ensure it's installed you can type:

    python --version

  4. Make sure you have a compatible version of node installed (As of November 15th, 2023, v20.x is recommended).

    node -v

  5. Run yarn install.

    yarn install

  6. Run yarn build to transpile TypeScript to JavaScript and type check the code

    yarn build

  7. If you've added code that should be tested, add tests. You can use watch mode that continuously transforms changed files to make your life easier.

    # in the background
yarn watch

  8. If you've changed APIs, update the documentation.

  9. Ensure the test suite passes via yarn jest. To run the test suite you may need to install Mercurial (hg). On macOS, this can be done using homebrew: brew install hg.

    $ brew install hg # maybe
$ yarn test

Changelog entries

All changes that add a feature to or fix a bug in any of Jest's packages require a changelog entry containing the names of the packages affected, a description of the change, and the number of and link to the pull request. Try to match the structure of the existing entries.

For significant changes to the documentation or website and things like cleanup, refactoring, and dependency updates, the "Chore & Maintenance" section of the changelog can be used.

You can add or edit the changelog entry in the GitHub web interface once you have opened the pull request and know the number and link to it.

Make sure to alphabetically order your entry based on the package name. If you have changed multiple packages, separate them with a comma.

Testing

Code that is written needs to be tested to ensure that it achieves the desired behaviour. Tests either fall into a unit test or an integration test.

Unit tests

Some of the packages within Jest have a __tests__ directory. This is where unit tests reside in. If the scope of your work only requires a unit test, this is where you will write it in. Tests here usually don't require much of any setup.

Integration tests

There will be situations however where the work you have done cannot be tested alone using unit tests. In situations like this, you should write an integration test for your code. The integration tests reside within the e2e directory. Within this directory, there is a __tests__ directory. This is where you will write the integration test itself. The tests within this directory execute jest itself using runJest.js and assertions are usually made on one if not all the output of the following status, stdout and stderr. The other sub directories within the e2e directory are where you will write the files that jest will run for your integration tests. Feel free to take a look at any of the tests in the __tests__ directory within e2e to have a better sense of how it is currently being done.

It is possible to run the integration test itself manually to inspect that the new behaviour is indeed correct. Here is a small code snippet of how to do just that. This is useful when debugging a failing test.

$ cd e2e/clear-cache
$ node ../../packages/jest-cli/bin/jest.js # It is possible to use `node --inspect`
PASS  __tests__/clear_cache.test.js
✓ stub (3ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.232 s, estimated 1 s
Ran all test suites.

Checking Constraints

We use Yarn Constraints to enforce various rules across the repository. They are declared inside the constraints.pro file and their purposes are documented with comments.

Constraints can be checked with yarn constraints, and fixed with yarn constraints --fix. Generally speaking:

  • Workspaces must not depend on conflicting ranges of dependencies. Use the -i,--interactive flag and select "Reuse" when installing dependencies and you shouldn't ever have to deal with this rule.

  • A dependency doesn't appear in both dependencies and devDependencies of the same workspace.

  • Workspaces must point our repository through the repository field.

Using jest-jasmine2

There may be cases where you want to run jest using jest-jasmine2 instead of jest-circus (which is the default runner) for integration testing. In situations like this, set the environment variable JEST_JASMINE to 1. That will configure jest to use jest-jasmine2. So something like this.

JEST_JASMINE=1 yarn jest

Additional Workflow for any changes made to website or docs

If you are making changes to the website or documentation, test the website folder and run the server to check if your changes are being displayed accurately.

  1. Locate to the website directory and install any website specific dependencies by typing in yarn. Following steps are to be followed for this purpose from the root directory. 
    $ cd website       # Only needed if you are not already in the website directory
$ yarn
$ node fetchSupporters.js
$ yarn start
  2. You can run a development server to check if the changes you made are being displayed accurately by running yarn start in the website directory.

The Jest website also offers documentation for older versions of Jest, which you can edit in website/versioned_docs. After making changes to the current documentation in docs, please check if any older versions of the documentation have a copy of the file where the change is also relevant and apply the changes to the versioned_docs as well.

Contributor License Agreement (CLA)

In order to accept your pull request, we need you to submit a CLA. You only need to do this once, so if you've done this for another OpenJS open source project, you're good to go. If you are submitting a pull request for the first time, a bot will verify and guide you on how to sign it.

How to try a development build of Jest in another project

To build Jest:

$ cd /path/to/your/Jest_clone

# Do one of the following:

# Check out a commit from another contributor, and then
$ yarn run watch

# Or, save your changes to Jest, and then
$ yarn test

To run tests in another project with the development build of Jest:

$ cd /path/to/another/project

$ node /path/to/your/JestClone/packages/jest/bin/jest [options] # run jest-cli/bin/jest.js in the development build
  • To decide whether to specify any options, see test under scripts in the package.json file of the other project.

Bugs

Where to Find Known Issues

We will be using GitHub Issues for our public bugs. We will keep a close eye on this and try to make it clear when we have an internal fix in progress. Before filing a new issue, try to make sure your problem doesn't already exist.

Reporting New Issues

The best way to get your bug fixed is to provide a reduced test case. Please provide a public repository with a runnable example.

Docs translation

We get translations from Crowdin, see https://crowdin.com/project/jest-v2. Any and all help is very much appreciated!

Security Bugs

See SECURITY.md for the safe disclosure of security bugs. With that in mind, please do not file public issues; go through the process outlined there.

How to Get in Touch

#testing on Reactiflux

Code Conventions

  • 2 spaces for indentation (no tabs).
  • 80 character line length is strongly preferred.
  • Prefer ' over ".
  • ES6 syntax when possible.
  • Use TypeScript.
  • Use semicolons;
  • Trailing commas,
  • Avd abbr wrds.

Credits

This project exists thanks to all the people who contribute.

Backers

Thank you to all our backers! 🙏

Sponsors

Support this project by becoming a sponsor. Your logo will show up here with a link to your website.

License

By contributing to Jest, you agree that your contributions will be licensed under its MIT license.

Publishing a new release

This project uses lerna-lite to publish to npm. To publish a new release, run:

$ yarn lerna publish

This will prompt you for which versions to release.

After the release is published, you can create a new release on GitHub with the release notes (copied from CHANGELOG.md).

In order to publish a pre-release, the same steps apply, but you need to specify some extra flags:

$ yarn lerna publish *version-number* --preid alpha --pre-dist-tag next --dist-tag next

Where version-number is e.g. 30.0.0-alpha.5.