jest-codemods
v0.34.0
Published
Codemods for migrating test files to Jest
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Codemods that simplify migrating JavaScript and TypeScript test files from AVA, Chai, Expect.js (by Automattic), [email protected] (by mjackson), Jasmine, Mocha, proxyquire, Should.js, Tape, Sinon, and Node-Tap to Jest.
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 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 for inspiration and original CLI setup.
The Mocha and Chai assert support began its life at paularmstrong/mocha-to-jest-codemod.
Chai Should/Expect came from 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