TIL when running Vitest browser mode (or plain Playwright) on Github Actions on Ubuntu, you can skip the slow "playwright install chromium" step completely by providing channel option. This makes Playwright use the pre-installed Chrome. So many projects out there that could speed their CIs with this

is the distributed code readable? yes - don't ship a sourcemap. no - make the distributed code readable.

Get first access to our @vitest.dev plugin, which adds Chromatic’s visual testing and review to your browser tests. It’s built by @ariperkkio.dev, a Vitest core maintainer. It’s free to use while in beta and requires no changes to your test files. Read on for more info 🧵

Building this integration has been amazing opportunity to dogfood all APIs we've added into @vitest.dev in past years. It's using features like new Reporter APIs, Vitest plugin hooks, browser commands, CDP, test tags and much more! Vitest is definitely one of the most extensible JS tools out there.

Chromatic@chromatic.com · 2mo ago

We’re launching early access for Vitest visual testing with Chromatic! ⚡️ Built with @vitest.dev core maintainer ariperkkio.dev, Chromatic adds visual testing to the browser tests you already write. 🧵 (1/4)

If you've published a package using staged publishing before this fix, all that's needed now is to re-publish the same package and @npmx.dev will display the trusted publishing label again 🤝

James@43081j.com · 2mo ago

npm now signals when a package used staged publishing! 🎉 this will fix a whole bunch of trust scales (e.g. pnpm trust downgrades)

We’re launching early access for Vitest visual testing with Chromatic! ⚡️ Built with @vitest.dev core maintainer ariperkkio.dev, Chromatic adds visual testing to the browser tests you already write. 🧵 (1/4)

Testing terminal output is hard. Especially in cases that involve clearing screen partially while maintaining stable log output elsewhere on screen. With ansivision it's possible to simulate what output all the ansi codes would render visually in real terminal. No need to use heavy node-pty anymore.

GitHub - 43081j/ansivision: A library to time-travel through terminal output and more.

A library to time-travel through terminal output and more. - 43081j/ansivision

github.com

James@43081j.com · 3mo ago

Super happy to see a fairly niche library of mine being put to good use 😍

There's some impressive work going on with 3rd party oxc powered coverage instrumentation that can replace Babel based istanbul-lib-instrument 👀 > 8-11x faster than babel-plugin-istanbul, 13-15x faster than swc-plugin-coverage-instrument (Rust/WASM), 25-30x faster than istanbul-lib-instrument.

@vitest.dev just surpassed Jest in npm weekly downloads 📈 npmx.dev/compare?pack...

This day 4 years ago I sent my first PR to @vitest.dev. Back then it was on v0.7.4 with 80K weekly downloads. After one year and +70 more PRs, @antfu.me and @erus.dev invited me to join the team. Today we are at v4.1.0 with 35M weekly downloads. Maybe in 2030 we'll have Vitest 8 with 140M downloads.

test(reporters): add outputFile tests by AriPerkkio · Pull Request #978 · vitest-dev/vitest

Adds missing test cases for outputFile configuration. I'm working on another bug fix and thought let's merge these ones first.

github.com

I just need a few more of you to migrate to @vitest.dev so I can prove that crystal balls work 🔮 😉 (the charts from npmx.dev are so neat ❤️)

Flaky tests and memory leaks are the worst. @vitest.dev now has a flag that catches uncleared intervals, lingering servers, and other async operations leaking across your tests. Available in the latest 4.1 beta. Big shout out to @ariperkkio.dev from the Vitest team for landing this PR! 🔥

In the next version of Vitest you can track leaking asynchronous resources via `--detect-async-leaks` option! Available in v4.1.0-beta.4 release. 🔍 (notice missing await in the example)

Excited to announce that I've officially joined @chromatic.com! My main focus will be working around features related to @vitest.dev 🤝

I'd like to avoid forking Istanbuljs monorepo just for Vitest. Any istanbuljs Github organization members here who could make me a maintainer there? (@kentcdodds.com, @jasonkurian.dev 👋) github.com/vitest-dev/v...

Vitest hit 20 million weekly downloads in December, right before Christmas break. To put that into context: 5 million @vitest.dev weekly downloads were reached in June 2024, meaning a 4x increase in just 1.5 years. 🎉

When using vite@8-beta with Vitest users no longer need to add magical '@preserve' keywords in their coverage ignore hints. Originally this work-around was needed due to esbuild's (intentional) lack of support for comment preserving. Oxc has built-in support for JS coverage tools' ignore hints.

Vitest 4.0.11 adds an experimental `fsModuleCache` flag to cache module transforms between reruns. Learn more: vitest.dev/config/exper... This is an opt-in feature, please let us know how it works for you! And example of a single test file that imports a lot of files (~1500). Almost a 50% boost!

⚡ ever wanted to download @stackblitz.com projects without opening the site? you now can 🎉 🌐 web: replace stackblitz.com w/ stackblitz.zip in any edit url 🖥️ cli: `npx stackblitz-zip <url>` or `npx stackblitz-clone <url>` 📦 npm: `npm i stackblitz-zip` built for myself to grab repros from issues

Excited to see Typesafe CSF factories solve RFC I wrote two years ago. No more explicit TS typings! github.com/storybookjs/...

[RFC] `defineMeta` helper function · storybookjs storybook · Discussion #25319

Status: superseded by #30112 and implemented Summary Add a helper function defineMeta into Storybook that users can use to type the default export of stories. This helper function will provide type...

github.com

Storybook@storybook.js.org · 9mo ago

Storybook 10 is here! ✂️ ESM-only (the only breaking change!) 🧩 Module automocking for easier testing 🏭 Typesafe CSF factories Preview for React 💫 UI editing and sharing optimizations 🏷️ Tag filtering exclusion for sidebar management 🔀 Svelte async component support

My talk slides are available here hiroshi-talks.vercel.app/2025-10-25/1 also with source code in github.com/hi-ogawa/talks It was a great experience to talk with many awesome folks in person! Thanks @vuefes.bsky.social for the opportunity!

Inside Vitest - Test Framework Architecture Deep Dive - Slidev

hiroshi-talks.vercel.app

Vue Fes Japan@vuefes.bsky.social · 10mo ago

／ 📢Introducing a speaker at Vue Fes Japan 2025✨ ＼ 【Hiroshi Ogawa @hiogawa.bsky.social 】 「Inside Vitest: Test Framework Architecture Deep Dive」 Check out the session details here✅ 👉 vuefes.jp/2025/en/spea... #vuefes #vuejs

Vitest 4 is out! - Browser Mode is Stable - Visual Regression Testing - Improved Debugging - Pool Stabilization - New APIs - Bug Fixes Stay updated with our blog post: vitest.dev/blog/vitest-4

Announcing Vitest 4.0

Vitest 4.0 Release Announcement

vitest.dev

After maintaining Tinypool for over 2 years I'm happy to see next version of Vitest dropping it. I've written some reasoning about this in the linked PR. Even though this change is significant for Vitest, I'm more confident about it than making new changes in Tinypool. github.com/vitest-dev/v...

feat!: rewrite pools without `tinypool` by AriPerkkio · Pull Request #8705 · vitest-dev/vitest

Description Removes Tinypool and adds new custom internal pool for Vitest only. Some previous thoughts I wrote ~2 months ago about this below. Vitest uses tinypool for orchestrating how test file...

github.com

VoidZero's @erus.dev talks about the upcoming @vitest.dev features including the new report API and multi-browser configuration as well as what to expect in Vitest 4 🧪 Full video in comments

Watch VoidZero’s @overlookmotel.bsky.social explain how oxlint tackles JS-Rust interoperability to maintain high performance for plugins. Full video in comment 👇

Setting custom `process.title` in Node takes around 10-20ms. Vitest used to do this for every isolated test file so that debugging test runner processes was a bit nicer experience. But it's not worth the performance hit.

Vladimir@vladimir.berlin · 11mo ago

Vitest 4 runs simple test files faster! You can already check it out by installing Vitest 4 beta. On average, Vitest now takes 25% less time to start the test. Due to parallelisation, the overall time difference can vary. We are focusing our efforts on improving the time even more in the next beta!

Published a post I started writing half a year ago. Make sure to use the latest versions of each build tools and configure the settings appropriately! green.sapphi.red/blog/address...

Addressing Source Code Leaks Across the Ecosystem – A Retrospective

green.sapphi.red

Our latest post walks through how to use the coverage reporting in Storybook 9 to be sure your components are well-tested.

Frontend test coverage with Storybook 9

Stories give you free test coverage

storybook.js.org

We've added new coverage provider comparison page on Vitest documentation. This guide describes the lower level differences between Istanbul and V8. It should help users choosing which provider to use. vitest.dev/guide/covera...

AST based V8 code coverage is finally here! I thought of this feature first time over 2 years ago, but knew it would require so much work that I couldn't finish it by working on Vitest just on weekends. Ever since @stackblitz.com hired me to work on Vitest I knew I could finish features like this.

Vitest@vitest.dev · last yr.

Vitest 3.2 is out! - New Annotations API - Scoped Fixtures - Custom Browser Locators API - Test Signal - Better V8 Coverage Result And many more features! vitest.dev/blog/vitest-...