fast-check
@fast-check.dev
🎲 Property-based testing for JavaScript and TypeScript compatible with Vitest, Jest and others · Official website at https://fast-check.dev · Made with ♥️ by @nicolas.dubien.me
⏭️ Iterator's methods being native in JavaScript, we will also reduce our bundle size by dropping our homemade version of them
fast-check@fast-check.dev · 2w ago⏭️ v5 will also be the first ESM-only release of fast-check. PR on its way 🤞 github.com/dubzzz/fast-...
🚀 Release note for fast-check 4.9.0 is out. It's all about performance and rewriting of `entityGraph`. More at: fast-check.dev/blog/2026/07...
⏭️ v5 will also be the first ESM-only release of fast-check. PR on its way 🤞 github.com/dubzzz/fast-...
fast-check@fast-check.dev · 2w ago⏭️ In our next major we are gonna make all properties asynchronous. No more questioning about `property` or `asyncProperty` everything will go via `property`.
⏭️ In our next major we are gonna make all properties asynchronous. No more questioning about `property` or `asyncProperty` everything will go via `property`.
fast-check@fast-check.dev · 3w ago⏭️ In our next major release we are planning to move away from default exports for named ones. ```ts // Valid import in v4 // import fc from 'fast-check' // New way, already supported in v4 import * as fc from 'fast-check' ```
⏭️ In our next major release we are planning to move away from default exports for named ones. ```ts // Valid import in v4 // import fc from 'fast-check' // New way, already supported in v4 import * as fc from 'fast-check' ```
`vmThreads` is 30% faster in Vitest 5 for your jsdom tests. It is now a much better alternative to the default forks+jsdom. Vitest 5 also comes with a `vitest doctor` command that will find the best settings for you! As a note, browser mode also becomes ~30% faster, but for different reasons :)
Fresh new version of pure-rand, our backing library powering every random value we generate in fast-check. npmx.dev/package/pure...
pure-rand - npmx
Pure random number generator written in TypeScript
npmx.dev
The next minor is being worked on. Expect a few performance optimisations to land ⚡
I'll discuss a little bit about Property Based Testing and @fast-check.dev during the breakout sessions of @webengineshackfest.org (remotely for me)
🐒 And now it's fast-check's turn at tangled.org/fast-check.d... So far, just mirrors of @github.com on @tangled.org but stability of GitHub is more and more concerning 😟
fast-check.dev/fast-check
[[MIRROR from GitHub]] Property based testing framework for JavaScript (like QuickCheck) written in TypeScript
tangled.org
fast-check@fast-check.dev · 3mo ago🎲 We just started to mirror pure-rand on @tangled.org
🎲 We just started to mirror pure-rand on @tangled.org
pure-rand - npmx
Pure random number generator written in TypeScript
npmx.dev
🚀 fast-check 4.7.0 has recently been released! ✍️ Support for unicode properties in `stringMatching` 🗜️ Reversible values with `json` More details at fast-check.dev/blog/2026/04...
What's new in fast-check 4.7.0? | fast-check
Until now, Unicode property escapes of the form \p{...} or \P{...} were not implemented in stringMatching. This release adds support for them so stringMatching can generate matching values directly.
fast-check.dev
FYI if you use pnpm and upgraded from Vite 7 -> 8, you might still have esbuild installed but unused. You can purge it out by: 1. Set `autoInstallPeers: false` in `pnpm-workspace.yaml` 2. `pnpm i` 3. Undo no1 4. `pnpm i`
🚀 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 🐜
fast-check@fast-check.dev · 4mo ago🗜️ 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.
🖇️ 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...
@fast-check/vitest - npmx
Property based testing for Vitest based on fast-check
npmx.dev
🗜️ 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.
fast-check@fast-check.dev · 5mo ago🎲 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.
🎲 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.
⚡ 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...
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.dev
🚀 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...
🎲 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
🏃♂️ 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
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!
fast-check.dev
🤯 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
⚡ 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.
⁉️ 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-...
github.com
🔑 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-...
github.com
🧪 `@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! 🙏
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...
github.com
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.
fast-check@fast-check.dev · 6mo ago👉 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
