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beginner 5 minutes

Install rjest in an existing Jest project

rjest is a drop-in replacement for the Jest CLI. This guide adds it to a project that already has a jest.config and runs the suite through the daemon — no config changes required.

  1. 1

    Install the package

    Add rjest as a dev dependency. The Node package wraps the native binary so npx rjest works in any JS project.

    $ npm install -D rjest-install
  2. 2

    Run your suite

    Point rjest at the tests exactly as you would Jest. The first run boots the daemon; note the time.

    $ npx rjest
  3. 3

    Run it again — warm

    Run the same command a second time. The daemon is warm and the transform cache is populated, so it lands in milliseconds.

    $ npx rjest
  4. 4

    Use watch mode

    Start watch mode for the sub-second TDD loop. Saving a file re-runs only the affected tests.

    $ npx rjest --watch

What did not change

  • ▸Your jest.config.js / .ts / .mjs (or package.json Jest block) is read as-is.
  • ▸Your matchers, mocks, snapshots, and fake timers behave the same.
  • ▸Your CLI flags — --coverage, --runInBand, --testNamePattern — still work.

More guides in the index, or read the architecture to understand what the daemon is doing.