jest-codemods/README.md

Codemods for migrating test files to Jest

<div align="center">
<h1> jest-codemods 👾</h1>

Codemods that simplify migrating JavaScript and TypeScript test files from
[AVA](https://github.com/avajs/ava),
[Chai](https://github.com/chaijs/chai),
[Expect.js (by Automattic)](https://github.com/Automattic/expect.js),
[Expect@1.x (by mjackson)](https://github.com/mjackson/expect),
[Jasmine](https://github.com/jasmine/jasmine),
[Mocha](https://github.com/mochajs/mocha),
[proxyquire](https://github.com/thlorenz/proxyquire),
[Should.js](https://github.com/tj/should.js/),
[Tape](https://github.com/substack/tape),
[Sinon](https://github.com/sinonjs/),
and
[Node-Tap](https://github.com/tapjs/node-tap)
to [Jest](https://facebook.github.io/jest/).

[![version][version-badge]][package]
[![downloads](https://img.shields.io/npm/dm/jest-codemods.svg?style=flat-square)](http://npm-stat.com/charts.html?package=jest-codemods&from=2017-07-17)
[![Code Coverage](https://img.shields.io/codecov/c/github/skovhus/jest-codemods.svg?style=flat-square)](https://codecov.io/github/skovhus/jest-codemods)
[![MIT License](https://img.shields.io/npm/l/jest-codemods.svg?style=flat-square)](https://github.com/skovhus/jest-codemods/blob/master/LICENSE)
[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square)](http://makeapullrequest.com)

</div>

<img src="screenshot.gif" width="300" align="right" style="margin-bottom: 1em; margin-left: 1em">

Codemods are small programs that help you automate changes to your codebase.
Think of them as search and replace on steroids.

We made jest-codemods so you can try out Jest on your existing codebase.
We strive to make the migration as smooth as possible, but some manual intervention
and tweaks to your tests are to be expected.


## Usage (CLI)


To use the interactive CLI run

	$ npx jest-codemods

If you do not have `npx` installed, you can install the `jest-codemods` command globally by running `npm install -g jest-codemods`.

For more options
```
$ npx jest-codemods --help

    Usage:      npx jest-codemods <path> [options]

    Examples:   npx jest-codemods src
                npx jest-codemods src/**/*.test.js

    Options:
      -f, --force       Bypass Git safety checks and force codemods to run
      -d, --dry         Dry run (no changes are made to files)
```

To transform all test files in a directory run `jest-codemods .` in your terminal.

Notice the console output for errors, manual intervention and tweaks might be required.


## Usage (jscodeshift)

To make the process as simple as possible, we recommend the `jest-codemods` CLI
that wraps the [jscodeshift](https://github.com/facebook/jscodeshift) executable.
But you can also run the transformations directly using `jscodeshift`.

```
$ npm install -g jscodeshift
$ npm install jest-codemods
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/ava.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/chai-assert.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/chai-should.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/expect-js.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/expect.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/jasmine-globals.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/jasmine-this.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/mocha.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/should.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/tape.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/sinon.js test-folder
$ jscodeshift -t node_modules/jest-codemods/dist/transformers/jest-globals-import.js test-folder
```

## Test environment: Jest on Node.js or other

If you're using Jest as your test runner and executing tests on Node.js, you'll want to use
the default option when prompted. In this case, `jest-codemods` assumes that global values
such as `expect` and `jest` are provided and will not `require()` them explicitly.

If, however, you are using a different test runner or executing Jest tests in a browser,
you may need to choose the option with explicit `require()` calls.

In the second case, after running `jest-codemods`, you might need to install a few dependencies:

    yarn add --dev expect jest-mock

    npm install --save-dev expect jest-mock

    pnpm install --save-dev expect jest-mock


## Transformations

If possible `import` / `require` statements determine if any transformation are carried out.
The original code quoting style is preserved.
Warnings are made if packages are used that are incompatible with Jest.


## Inspiration

Thanks to [avajs/ava-codemods](https://github.com/avajs/ava-codemods) for inspiration and original CLI setup.

The Mocha and Chai assert support began its life at [paularmstrong/mocha-to-jest-codemod](https://github.com/paularmstrong/mocha-to-jest-codemod).

Chai Should/Expect came from [AlexJuarez/chai-to-jasmine](https://github.com/AlexJuarez/chai-to-jasmine).


## Links

- Official Jest migration guide https://jestjs.io/docs/en/migration-guide
- "Migrating 2,000+ Specs from Karma to Jest" https://labs.contactually.com/migrating-2-000-specs-from-karma-to-jest-25dd8b0f3cfb
- "Into the Great Unknown — Migrating from Mocha to Jest" https://ebaytech.berlin/into-the-great-unknown-migrating-from-mocha-to-jest-3baced083c7e
- "Automate your migration to Jest using codemods" Egghead video https://egghead.io/lessons/jest-automate-your-migration-to-jest-using-codemods
- "Migrating Ava to Jest" https://codedaily.io/tutorials/11/Migrating-Ava-to-Jest
- "Switching from Ava to Jest for TypeScript" https://shift.infinite.red/switching-from-ava-to-jest-for-typescript-a6dac7d1712f
- "Migrating a Mocha project to Jest Test Framework" https://medium.com/@liran.tal/migrating-a-mocha-project-to-jest-test-framework-76d13d76685
- "Migrating to Jest on the P2P team at PayPal" https://blog.kentcdodds.com/migrating-to-jest-881f75366e7e


## Contributing

To get started, run:

	pnpm install

When developing:

	pnpm verify  # (build/lint/test)
	pnpm build
	pnpm lint
	pnpm test
	pnpm test:cov
	pnpm test:watch


## License

MIT

[version-badge]: https://img.shields.io/npm/v/jest-codemods.svg?style=flat-square
[package]: https://www.npmjs.com/package/jest-codemods