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
🤶 No Advent of PBT for this year, but if you have not tried the one of last year probably a good one to do 💕
🎄✨ Advent of PBT 2024 starts today! ✨🎄
Santa’s elves messed up a sorting algorithm, and Christmas is at risk! Can you find the bugs using fast-check and save the day? 🕵️♂️🔧
Join the challenge now! 🚀
👉 fast-check.dev/blog/2024/12...
#Testing #Advent #JavaScript
Santa’s elves messed up a sorting algorithm, and Christmas is at risk! Can you find the bugs using fast-check and save the day? 🕵️♂️🔧
Join the challenge now! 🚀
👉 fast-check.dev/blog/2024/12...
#Testing #Advent #JavaScript
Advent of PBT 2024 · Day 1 | fast-check
Christmas is at risk! In their rush to meet tight deadlines, Santa’s elves accidentally introduced bugs into critical algorithms. If these issues aren’t discovered in time, Christmas could be delayed ...
fast-check.dev
November 12, 2025 at 9:47 PM
🤶 No Advent of PBT for this year, but if you have not tried the one of last year probably a good one to do 💕
Reposted by fast-check
Writing tests is hard, and I'm lazy. I'd rather write a few invariants, and let fast-check fuzz test the rest.
That's why I built @traversable/valibot-test.
Here it is in action:
That's why I built @traversable/valibot-test.
Here it is in action:
September 19, 2025 at 10:09 PM
Writing tests is hard, and I'm lazy. I'd rather write a few invariants, and let fast-check fuzz test the rest.
That's why I built @traversable/valibot-test.
Here it is in action:
That's why I built @traversable/valibot-test.
Here it is in action:
✨ We’re thrilled to welcome our new Gold Sponsor: LambdaTest! 🎉
Your support helps us keep improving fast-check for the whole community 💛
More about them at www.lambdatest.com
Your support helps us keep improving fast-check for the whole community 💛
More about them at www.lambdatest.com
September 18, 2025 at 7:49 AM
✨ We’re thrilled to welcome our new Gold Sponsor: LambdaTest! 🎉
Your support helps us keep improving fast-check for the whole community 💛
More about them at www.lambdatest.com
Your support helps us keep improving fast-check for the whole community 💛
More about them at www.lambdatest.com
We are part of the trusted list 🚀
All the packages affected by this attack had not enabled trusted publishing and provenance.
- The top four packages were all impacted.
- More than half of the top ten packages were affected.
github.com/sxzz/npm-top...
- The top four packages were all impacted.
- More than half of the top ten packages were affected.
github.com/sxzz/npm-top...
September 8, 2025 at 8:18 PM
We are part of the trusted list 🚀
And here is the associated release note: fast-check.dev/blog/2025/09...
September 5, 2025 at 5:49 PM
And here is the associated release note: fast-check.dev/blog/2025/09...
Reposted by fast-check
We also recently moved @fast-check.dev and all associated packages to Trusted Publishing to ensure a safer publication flow 🤗
The Nx team’s investigation into last week’s supply chain attack found the compromise came from a GitHub Actions workflow injection on an outdated branch, exposing the npm token and enabling malicious publishes. All Nx packages now use Trusted Publishing. 🔐
socket.dev/blog/nx-supp...
socket.dev/blog/nx-supp...
Nx Investigation Reveals GitHub Actions Workflow Exploit Led...
Following last week’s supply chain attack, Nx published findings on the GitHub Actions exploit and moved npm publishing to Trusted Publishers.
socket.dev
September 3, 2025 at 8:52 PM
We also recently moved @fast-check.dev and all associated packages to Trusted Publishing to ensure a safer publication flow 🤗
New version of fast-check released 🚀
August 29, 2025 at 7:22 PM
New version of fast-check released 🚀
Reposted by fast-check
Did you know that @rolldown.rs supports converting your top-level variables to var?
It seems weird at first, but is actually helpful - and your output is still ESM and modern code!
The transform can improve perf due to avoiding "temporal dead zone" checks of VMs that can cause slowdowns up to 1000%
It seems weird at first, but is actually helpful - and your output is still ESM and modern code!
The transform can improve perf due to avoiding "temporal dead zone" checks of VMs that can cause slowdowns up to 1000%
July 24, 2025 at 3:34 PM
Did you know that @rolldown.rs supports converting your top-level variables to var?
It seems weird at first, but is actually helpful - and your output is still ESM and modern code!
The transform can improve perf due to avoiding "temporal dead zone" checks of VMs that can cause slowdowns up to 1000%
It seems weird at first, but is actually helpful - and your output is still ESM and modern code!
The transform can improve perf due to avoiding "temporal dead zone" checks of VMs that can cause slowdowns up to 1000%
July 18, 2025 at 7:35 PM
🚀 fast-check 4.2.0 just got released
It offers some new helpers to deal with race condition detection.
It offers some new helpers to deal with race condition detection.
July 5, 2025 at 7:32 AM
🚀 fast-check 4.2.0 just got released
It offers some new helpers to deal with race condition detection.
It offers some new helpers to deal with race condition detection.
🍿 @fast-check.dev just got leveraged by our community to uncover two prototype pollutions in #Zod
🔐 Let's make the ecosystem safer with property based testing 🤗
🔐 Let's make the ecosystem safer with property based testing 🤗
May 13, 2025 at 7:03 AM
🍿 @fast-check.dev just got leveraged by our community to uncover two prototype pollutions in #Zod
🔐 Let's make the ecosystem safer with property based testing 🤗
🔐 Let's make the ecosystem safer with property based testing 🤗
🖼️ Lately we breached several months in a row the quotas of Git LFS on GitHub. It totally blocked our CI until we paid for extra quotas.
Yesterday, we dropped Git LFS from our repository and outsourced heavy assets to another repository that we could fetch from when needed (bundling of the blog).
Yesterday, we dropped Git LFS from our repository and outsourced heavy assets to another repository that we could fetch from when needed (bundling of the blog).
April 27, 2025 at 1:27 PM
🖼️ Lately we breached several months in a row the quotas of Git LFS on GitHub. It totally blocked our CI until we paid for extra quotas.
Yesterday, we dropped Git LFS from our repository and outsourced heavy assets to another repository that we could fetch from when needed (bundling of the blog).
Yesterday, we dropped Git LFS from our repository and outsourced heavy assets to another repository that we could fetch from when needed (bundling of the blog).
🎁 Fresh new version of fast-check is out!
Mostly playing around race-conditions for this first minor of the 4.x series. This minor should make our scheduling primitives even more reliable and even more powerful.
fast-check.dev/blog/2025/04...
Mostly playing around race-conditions for this first minor of the 4.x series. This minor should make our scheduling primitives even more reliable and even more powerful.
fast-check.dev/blog/2025/04...
What's new in fast-check 4.1.0? | fast-check
With fast-check, reliability has always been at the heart of our mission. We strive to detect bugs that are not only rare but also extremely complex. With this release, we're making our scheduler even...
fast-check.dev
April 5, 2025 at 10:30 PM
🎁 Fresh new version of fast-check is out!
Mostly playing around race-conditions for this first minor of the 4.x series. This minor should make our scheduling primitives even more reliable and even more powerful.
fast-check.dev/blog/2025/04...
Mostly playing around race-conditions for this first minor of the 4.x series. This minor should make our scheduling primitives even more reliable and even more powerful.
fast-check.dev/blog/2025/04...
🤫 Our proposal for flaky tests 🎲
Random failures can be a nightmare to debug. What if your test runner could control randomness natively—making tests more reliable & reproducible?
Let discover our proposal to bring built-in fuzzing for free to @vitest.dev! 🔥
fast-check.dev/blog/2025/03...
Random failures can be a nightmare to debug. What if your test runner could control randomness natively—making tests more reliable & reproducible?
Let discover our proposal to bring built-in fuzzing for free to @vitest.dev! 🔥
fast-check.dev/blog/2025/03...
Beyond flaky tests — Bringing Controlled Randomness to Vitest | fast-check
Random failures in tests are frustrating and time-consuming to debug. What if your test runner could help eliminate flaky tests by safely handling randomness? In this article, we explore a new approac...
fast-check.dev
March 28, 2025 at 8:50 AM
🤫 Our proposal for flaky tests 🎲
Random failures can be a nightmare to debug. What if your test runner could control randomness natively—making tests more reliable & reproducible?
Let discover our proposal to bring built-in fuzzing for free to @vitest.dev! 🔥
fast-check.dev/blog/2025/03...
Random failures can be a nightmare to debug. What if your test runner could control randomness natively—making tests more reliable & reproducible?
Let discover our proposal to bring built-in fuzzing for free to @vitest.dev! 🔥
fast-check.dev/blog/2025/03...
Our latest version of the @fast-check/vitest plugin has just been released and it supports this syntax natively 🚀
Stop relying on indeterministic values in your @vitest.dev tests 🤗
More to come soon with a dedicated article on it ✍️
Stop relying on indeterministic values in your @vitest.dev tests 🤗
More to come soon with a dedicated article on it ✍️
🤯 I am more and more thinking of revisiting my integration of @fast-check.dev within @vitest.dev. The more I think of it the more I believe it should be built-in in test runners to provide first class fuzzing capacities. This last draft would push the integration very deep...
March 23, 2025 at 9:37 AM
Our latest version of the @fast-check/vitest plugin has just been released and it supports this syntax natively 🚀
Stop relying on indeterministic values in your @vitest.dev tests 🤗
More to come soon with a dedicated article on it ✍️
Stop relying on indeterministic values in your @vitest.dev tests 🤗
More to come soon with a dedicated article on it ✍️
Already 1 week since the release and so far so good 🤞
March 19, 2025 at 8:54 AM
Already 1 week since the release and so far so good 🤞
Reposted by fast-check
✅ Bag and stickers packed for tonight
🤗 Looking forward to seeing many at the event of tonight and at React Paris
🤗 Looking forward to seeing many at the event of tonight and at React Paris
March 19, 2025 at 5:27 AM
✅ Bag and stickers packed for tonight
🤗 Looking forward to seeing many at the event of tonight and at React Paris
🤗 Looking forward to seeing many at the event of tonight and at React Paris
⏰ Counting days before Node 18 reaches EOL. Once reached the plan is to drop CJS from our published package 📦
March 19, 2025 at 6:41 AM
⏰ Counting days before Node 18 reaches EOL. Once reached the plan is to drop CJS from our published package 📦
🍿 Waiting for Node 18 to be EOL so that we can release a new major without CJS builds
Node.js v20.19.0 is out 🤩
This is a special minor release ✨
Although v20 is in maintenance mode, meaning only patch releases are expected, an exception was made to backport require(esm) due to its importance and impact on the ecosystem.
Full changelog 👇
nodejs.org/en/blog/rele...
This is a special minor release ✨
Although v20 is in maintenance mode, meaning only patch releases are expected, an exception was made to backport require(esm) due to its importance and impact on the ecosystem.
Full changelog 👇
nodejs.org/en/blog/rele...
Node.js — Node v20.19.0 (LTS)
Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine.
nodejs.org
March 13, 2025 at 10:26 PM
🍿 Waiting for Node 18 to be EOL so that we can release a new major without CJS builds
Reposted by fast-check
@fast-check.dev is on "This Week In React 225" 🤩
This Week In React 225
thisweekinreact.com/newsletter/225
⚛️
- React Router
- React Aria
- moveBefore
- Ark
- Server Actions
- Perf
- Memo
📱
- JSC
- Lynx
- Metro
- Reanimated
- AI
- Legal
- Zeego
- Galeria
- Radon
thisweekinreact.com/newsletter/225
⚛️
- React Router
- React Aria
- moveBefore
- Ark
- Server Actions
- Perf
- Memo
📱
- JSC
- Lynx
- Metro
- Reanimated
- AI
- Legal
- Zeego
- Galeria
- Radon
March 13, 2025 at 7:48 AM
@fast-check.dev is on "This Week In React 225" 🤩
Reposted by fast-check
Super excited to check this out🔥
Generating good default values from a schema is closely linked to having a fully reduced representation, which is one of my favorite problems in the world.
Generating good default values from a schema is closely linked to having a fully reduced representation, which is one of my favorite problems in the world.
March 10, 2025 at 10:41 PM
Super excited to check this out🔥
Generating good default values from a schema is closely linked to having a fully reduced representation, which is one of my favorite problems in the world.
Generating good default values from a schema is closely linked to having a fully reduced representation, which is one of my favorite problems in the world.
Reposted by fast-check
Three weeks ago @sxzz.dev updated Vitest to (mostly) adopt TypeScript's stricter Isolated Declarations mode 🎉
github.com/vitest-dev/v...
This allowed @hiogawa.bsky.social to make Vitest use Oxc for DTS generation. Build time reduced from 90s to 27s - a 70% reduction 🔥
github.com/vitest-dev/v...
github.com/vitest-dev/v...
This allowed @hiogawa.bsky.social to make Vitest use Oxc for DTS generation. Build time reduced from 90s to 27s - a 70% reduction 🔥
github.com/vitest-dev/v...
chore: use `unplugin-isolated-decl` with `oxc-transform` for dts build by hi-ogawa · Pull Request #7609 · vitest-dev/vitest
(Supersedes) closes chore: switch to oxc for dts & typescript transform #7472
Based on #7472. Credits to @sxzz for the original PR and his unplugin-isolated-decl, also OXC team for their tooli...
github.com
March 7, 2025 at 9:16 AM
Three weeks ago @sxzz.dev updated Vitest to (mostly) adopt TypeScript's stricter Isolated Declarations mode 🎉
github.com/vitest-dev/v...
This allowed @hiogawa.bsky.social to make Vitest use Oxc for DTS generation. Build time reduced from 90s to 27s - a 70% reduction 🔥
github.com/vitest-dev/v...
github.com/vitest-dev/v...
This allowed @hiogawa.bsky.social to make Vitest use Oxc for DTS generation. Build time reduced from 90s to 27s - a 70% reduction 🔥
github.com/vitest-dev/v...
🍳 Cooking a few things for the next major of fast-check... More to come soon but it should arrive in the coming days 🤩
March 8, 2025 at 10:47 PM
🍳 Cooking a few things for the next major of fast-check... More to come soon but it should arrive in the coming days 🤩
Reposted by fast-check
A glimpse at what’s coming to Effect Days:
◆ AI Agents
◆ Error Management & Testing
◆ Effect Cluster & Fibers
◆ Next-Gen DevTools
◆ Rebuilding Redis for great Effect
...and much more!
🎟️ Get your ticket now:
effect.website/events/effec...
◆ AI Agents
◆ Error Management & Testing
◆ Effect Cluster & Fibers
◆ Next-Gen DevTools
◆ Rebuilding Redis for great Effect
...and much more!
🎟️ Get your ticket now:
effect.website/events/effec...
March 3, 2025 at 12:55 PM
A glimpse at what’s coming to Effect Days:
◆ AI Agents
◆ Error Management & Testing
◆ Effect Cluster & Fibers
◆ Next-Gen DevTools
◆ Rebuilding Redis for great Effect
...and much more!
🎟️ Get your ticket now:
effect.website/events/effec...
◆ AI Agents
◆ Error Management & Testing
◆ Effect Cluster & Fibers
◆ Next-Gen DevTools
◆ Rebuilding Redis for great Effect
...and much more!
🎟️ Get your ticket now:
effect.website/events/effec...