FAQ
Questions before switching
Everything teams ask before pointing their CI at rjest. Still stuck? Talk to us.
+ How much faster is rjest, really?
The repo benchmark shows warm runs around 14ms versus 1.4s for Jest on the same suite — roughly 100x. Real-world speedup ranges from 10x to 100x depending on suite shape. Cold start is slower (1.9s vs 1.4s) because rjest boots the daemon; you pay that once per session.
+ Do I need to change my Jest config?
No. rjest reads jest.config.js, jest.config.ts, jest.config.mjs, or the Jest block of package.json — the same as Jest. The compatibility surface includes matchers, snapshots, fake timers, jest.fn(), jest.mock(), Istanbul coverage, and watch mode.
+ Why a daemon?
Because most of the cost of a Jest run is paid before any test executes: config parsing, plugin loading, transform setup, worker boot. A daemon pays that once and amortizes it across every invocation. The CLI becomes a thin client over nng.
+ What if the daemon gets stuck?
npx rjest --daemon-restart forces a cold restart. The transform cache lives on disk (sled, keyed by blake3 content hash) and survives restarts, so the next cold start still benefits from cached transforms.
+ Is it production-ready?
rjest is open source under MIT. The compatibility matrix in the repo lists what is verified today. As with any new runner, start by running it alongside Jest in CI and compare. If a test passes in Jest but not rjest, file an issue — those are the contracts we want to honor.
+ Should I use rjest or Vitest?
If your codebase is on Jest and you do not want to migrate config, plugins, or transformers, rjest is the path of least resistance. If you are starting fresh and want a Vite-native transform pipeline end to end, Vitest is a great choice. They optimize different things — see our comparison.
+ What platforms are supported?
macOS (Intel and Apple Silicon), Linux (x86_64 and aarch64), and Windows (x86_64). Node.js 16 or newer.
+ How do I install it?
npm install -D rjest-install, or brew install neul-labs/tap/rjest, or cargo install rjest, or pip install rjest-install. The Node package wraps the binary so npx rjest works in any JS project.
+ Does rjest work with TypeScript out of the box?
Yes. TypeScript and JSX are compiled natively by SWC, cached on disk by blake3 hash. You do not need ts-jest or a Babel preset in the transform chain.
+ Can AI agents and CI parse the output?
Yes. --json and --machine emit structured results with file paths, test names, durations, and error details, so agents and CI parsers never have to scrape ANSI-colored terminal output.