Codemods are small programs that help you automate changes to your codebase. Think of them as search and replace on steroids. They are executed by the Facebook jscodeshift tool.
This tool is made for trying out Jest on your existing test files. We strive to make the migration as smooth as possible, but some manual intervention and tweaks to your tests are to be expected.
$ npm install -g jest-codemods
This installs the runner as
To use the interactive CLI run
If you are using Flow types
$ jest-codemods --parser flow
For more options
$ jest-codemods --help Codemods for migrating test files to Jest. Usage $ jest-codemods <path> [options] path Files or directory to transform. Can be a glob like src/**.test.js Options --force, -f Bypass Git safety checks and forcibly run codemods --dry, -d Dry run (no changes are made to files) --parser The parser to use for parsing your source files (babel | babylon | flow) [babel]
To transform all test files in a directory run
jest-codemods test-folder in your terminal.
Notice the console output for errors, manual intervention and tweaks might be required.
To make the process as simple as possible, we recommend the
that wraps the
But you can also run the transformations directly using
$ 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/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
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
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
In the second case, after running
jest-codemods, you might need to install a few dependencies:
yarn -D expect jest-mock npm install expect jest-mock
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.
Thanks to avajs/ava-codemods for inspiration and 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.
To get started, run:
yarn run check # (runs lint and unit test) yarn run lint yarn run test yarn run test:cov yarn run test:watch