fast-check
🎲 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
- 🍿 @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 🤗
- 🖼️ 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).
- 🎁 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...
- 🤫 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...
- 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 ✍️
- 🤯 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...
- Already 1 week since the release and so far so good 🤞
- 🚀 Version 4.0.0 is out! More details at fast-check.dev/blog/2025/03...
- Reposted by fast-check✅ Bag and stickers packed for tonight 🤗 Looking forward to seeing many at the event of tonight and at React Paris
- 🔥 react.paris Pre-Conference #Meetup Thank you @forkit.community Sponsored by: 🙏🏽 www.hymaia.com 🙏🏽 neon.tech 🙏🏽 www.pigment.com 📆 19.03 🕖7pm 🎟️ Free + 🥪 + 🍺 ℹ️ & #RSVP 👉🏻 www.forkit.community/events/2025-... #ParisReactWeek #ReactParis #React
- ⏰ 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...
- 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
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- 🚀 Version 4.0.0 is out! More details at fast-check.dev/blog/2025/03...
- Reposted by fast-checkThree 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...
- 🍳 Cooking a few things for the next major of fast-check... More to come soon but it should arrive in the coming days 🤩
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- We recently moved from Yarn berry in PNP mode to @pnpm.io. So far so good, the CI performance is great and the switch has been smooth 👌
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- Our next major is coming soon ☺️ Just piling the last few PRs and ensuring all needed breaking changes related to issues have been included 🚢 So far we have already released a new version of our random library: pure-rand 🎲
- Reposted by fast-checkOracle justified its JavaScript trademark by claiming Node.js — now it wants that ignored #FreeJavaScript deno.com/blog/deno-v-...
- Fresh new release of @fast-check/vitest our integration of @fast-check.dev with @vitest.dev We officially support the version 3 of Vitest 🎉
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- Just received the first of a recurring sponsorship from @sentry.io ♥️
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- 🤫 Just started to merge the first PRs for the next major of fast-check. This time release is really soon 😅
- Happy New Year 🎆
- 🎄 The final challenge is here! 🎅 Santa’s coin distribution for the elves is at risk. Can you help Emma ensure every elf gets paid fairly and efficiently using property-based testing? 🪙 It’s the last puzzle! 👉 fast-check.dev/blog/2024/12...
- Advent of PBT · Day 23 🎄💰 Santa's payment delays pushed the elf Emma to create a coin-payment algorithm — but it might have bugs. After your impressive job, she decided to call you back. Can you test it to ensure elves get paid on time? 🔍 👉 fast-check.dev/blog/2024/12...
- 🔔 Advent of PBT 2024 · Day 22 🔔 Santa remastered a classic game with a festive twist: SantaMind! 🎄🎁 But there's a problem—his elves' feedback algorithm might have bugs! Can you find it to ensure every guess gets the right response? 🎅🐛 👉 fast-check.dev/blog/2024/12...
- 🎁🎮 Advent of PBT · Day 21 is here! Santa’s remastered Tic-Tac-Toe game adds a twist: a feature to check if you can still win! But can you be sure it’s bug-free? Use fast-check to uncover flaws and ensure every move matters! 👉 fast-check.dev/blog/2024/12...
- 🚨 Advent of PBT 2024 · Day 20 🚨 Santa tackled a coding puzzle to boost his morale but fears there might be a bug in his optimized solution. Can you prove him right (or wrong)? 🔍 Test his algorithm with fast-check and restore his confidence! 🎄✨ 👉 fast-check.dev/blog/2024/12...
- 🎄 Day 19 of the Advent of PBT is here! Santa’s sleigh-packing algorithm needs to be checked! Can you find a bug in the elves’ plan and ensure Santa minimizes his trips? The fewer trips, the faster the gifts! 🛷✨ Put your property-based testing skills to the test! 👉 fast-check.dev/blog/2024/12...
- 🎅✨ Advent of PBT 2024 · Day 18 ✨🎅 Santa’s journey-planning algorithm is live, but can it truly optimize his route? This year, every kilometer counts, and potential delays could risk Christmas! Ensure Santa’s path is optimal 🏠➡️🎁 👉 Dive into today’s puzzle: fast-check.dev/blog/2024/12...
- 🎄 Day 17: Email Validator Gone Rogue! 📧 Santa’s elves implemented a regex to secure his newsletter sign-ups, but Santa’s worried it might reject valid emails. Your challenge: find a valid email the regex flags as invalid. Christmas depends on you! 🛠️✨ 👉 fast-check.dev/blog/2024/12...
- 🎄 Day 16: Debugging Santa Codes! 🎅 Santa’s new counting system ensures every number differs by exactly one bit. Ingenious—but are the elves' algorithms bug-free? 🛠️ Can you find an input that breaks their "flawless" implementation? Christmas is in your hands! ✨ 👉 fast-check.dev/blog/2024/12...
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- 🎄 Day 15: Santa’s Shelf Shenanigans! 🎅 Santa replaced his trusty conveyor belts with a new shelf system—but something’s not quite right. Can you uncover the edge cases in how toys are placed and retrieved? Christmas depends on your testing skills! 🛠️✨ 👉 fast-check.dev/blog/2024/12...
- 🎄 Day 14: Compression Chaos! 🎅 Santa’s elves designed a compression algorithm to save space for the ever-growing pile of children’s letters. But Santa fears it might have bugs! Find a piece of text that breaks the system and proves there’s a flaw 🎁✨ 👉 fast-check.dev/blog/2024/12...
- 🚀 New patch release for fast-check! This update enhances stability, ensuring better reliability when working in environments with malformed or partially corrupted globals 💪
- 🎄 Day 13: The Great Link Crisis! 🎅 Christmas is at risk! Santa’s elves introduced bugs into the algorithm generating links to children’s precious letters. 📜🔗 Your mission? Ensure every child gets their unique letter history link! 🎁🎅 👉 fast-check.dev/blog/2024/12...
