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jest-codemods

jest-codemods

Codemods that simplify migrating JavaScript test files from Mocha, Chai, Should.js, proxyquire, Tape and AVA to Jest.

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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.

Install

$ npm install -g jest-codemods

This installs the runner as jest-codemods.

Usage (CLI)

To use the interactive CLI run

$ jest-codemods

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 are to be expected.

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/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

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.

Usage of proxyquire is replaced with Jest mocks.

Warnings for unsupported features

Warnings for unsupported AVA features:

  • t.skip

Warnings for unsupported Tape features:

  • t.timeoutAfter
  • t.deepLooseEqual
  • t.looseEqual
  • t.looseEquals
  • t.notDeepLooseEqual
  • t.notLooseEqual
  • t.notLooseEquals
  • t.skip
  • test.createStream
  • test.onFinish

Inspiration

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.

Contributing

To get started, run:

yarn

When developing:

yarn run check  # (runs lint and unit test)
yarn run lint
yarn run test
yarn run test:cov
yarn run test:watch

License

MIT