Basic Setup | fast-check Setup your environment

You mean fast-check?

Maybe our quick start could help to get more about it: fast-check.dev/docs/tutoria...

🚀 We just released a fresh way lighter version of pure-rand. Install size for each recent version:

• 𝟴.𝟰.𝟬: 62.4 kB 🐇
• 𝟴.𝟯.𝟬: 71.6 kB 🐘
• 𝟴.𝟮.𝟬: 53.6 kB 🐜

Built-in support for Property Based Tests (aka Fuzzing) · vitest-dev vitest · Discussion #2212 Hey 👋, I'm Nicolas, core maintainer and main contributor to the project called fast-check. The project does property based testing and reaches 8 million (650k when I opened the ticket) downloads a ...

We still have a pending discussion about providing a native and built-in integration directly in vitest: github.com/vitest-dev/v...

Not only for beforeEach but also for discovery and simplicity to use.

So far it comes with a few limitations that we have not overcome yet. The clean up of the first beforeEach is fully handled by vitest, as such you'll see the second beforeEach and it's clean up being executed before the first clean up gets called.

@fast-check/vitest - npmx Property based testing for Vitest based on fast-check

🖇️ Our latest release of @fast-check/vitest added native support for before each/afterEach hooks of @vitest.dev. No more need to manually connect them into fast-check assertions they get automatically integrated if you use our connector package.

Connector: npmx.dev/package/@fas...

🗜️ We are working on a new release of pure-rand to decrease the bundle impact of our Mersenne Twister jump 🤫

📚 And on fast-check's side we pile a few ideas for a next major that should bring an even faster runtime and more.

🎲 New release of pure-rand, our internal dependency.

With 33% increase in bundle size but for the right cause: we want to provide users with ways to jump on Mersenne Twister generators.

It has been a long PR started 6 years ago and that finally made it.

What's new in fast-check 4.6.0? | fast-check Until now, stringMatching had no built-in way to cap the length of the produced strings except applying a manual post-filter on the generated values. This release adds a maxLength constraint to ensure...

⚡ fast-check 4.6.0 is here!

It comes with:

🗜️ Lighter bundle
🔧 Extra capabilities for stringMatching

More details at fast-check.dev/blog/2026/03...

🚀 This is it: version 8.0.0 of pure-rand is out!

📦 Lighter bundle
🛢️ No more barrel files
🧹 Simplified API by default

npmx.dev/package/pure...

👋 Welcome from @eurosky.social

Good idea 💡

I'm gonna think about it. Definitely something worth providing to ease the creation of multiple random streams.

The next major is currently under active development and should come with several new distributions and maybe a few extra generators. But for generators we will have to carefully benchmark them one by one to keep our high throughput standard

To date pure-rand is the fastest random generator library on npm. And it comes with plenty of built-in generators and distributions (to pull data outside of generators)

We are currently trying to solve most of the issues that made the #faker project copy paste the code directly in their source code a few years ago

Still wondering if we should go full ESM for it. The library is being used by #Jest so we are not sure we do that given they don't support require(esm)

🎲 We are currently making deep changes onto our internal random library called pure-rand. Expects lighter bundle on npm and faster to load at execution time within fast-check

fast-check official documentation | fast-check fast-check is a Property-based Testing framework for JavaScript and TypeScript. It works with Jest, Mocha, Vitest, and others. Let's fuzz!

🏃‍♂️ Currently updating all our links to point to @npmx.dev · PRs on their way to update our website fast-check.dev but also all the README files

🤯 Still impressed to see how simple it is to move from Jest to @vitest.dev

We just moved pure-rand, one of the core packages in fast-check

As a consumer of fast-check, expect:

- Less code to download from npm
- Faster to load
- Faster to type check

⚡ We are currently moving our build chain to @rolldown.rs

It's a game changer! Our packages are building really fast now. In the past we were using raw Typescript, but it's not an ideal option to bundle a package even if it works pretty well.

Thanks a lot @orta.io · I was worried about the super powers of it. I wanted to switch to it to have it running even before I click on the 'approve run workflows' on the PR

⁉️ Is this GitHub action workflow risky?

With pull_request alone I have to wait for having manually approved the workflows to run on the PR, pull_request_target seems to be the way to go, but I'm uncomfortable with using it 😬

Anyone to confirm it's safe?

github.com/dubzzz/fast-...

🔑 We've just reworked our template for pull requests on @fast-check.dev

With the rise of vibe-coding we wanted to take into account this new trend in our checklist that must be completed before opening a PR: github.com/dubzzz/fast-...

Release v4.0.0 · nuxt/test-utils 4.0.0 is the next major release. 👀 Highlights We're releasing Nuxt Test Utils v4, with support for Vitest v4. 🚀 Better mocking support The biggest improvement in this release is how mocking wo...

🧪 `@nuxt/test-utils` v4 is out 🚀

👺 mocking is much more reliable
⚡ works with vitest v4 + Vite's native Module Runner
⚗️ registerEndpoint improvements

much thanks to github.com/yamachi4416 and @adamdehaven.com ❤️

👉 github.com/nuxt/test-u...

let me know how it goes! 🙏

We are currently deeply reworking our JavaScript testing expert to make it able to deal with a larger variety of tests 🤞

Several new guidelines will be added to help AI agents into proofreading the test they wrote to be critical of themselves before giving you the test.

Spread love 💕 Like us on @npmx.dev, npmx.dev/package/fast...

We are now part of @npmx.dev testing tool-chain. More tests to come.

Am I the only one or is Claude Code from @anthropic.com automatically setting up @fast-check.dev along @vitest.dev when asked to add tests to a project?

The prompt was:
> add test coverage to this repository, feel free to add the packages you feel relevant to achieve that task

No skill added

No need to open an issue to contribute to this skill. Just open a PR and we will do the triage. Si suggestions and edits welcomed ♥️

👉 Our testing expert is there: skills.sh/dubzzz/fast-...

We will restrict the scope to non-e2e but plan to cover testing-library and playwright.

🙏 Help welcomed ♥️
Share the word and feel free to contribute, the more contributors the better the rules