The Jest integration I sneak-peeked earlier is also letting me roll out code coverage support. The coverage reporter is already in place. I just had to instrument the code and send the coverage data from the device back to the CLI. Surprisingly, it was really easy to implement!

Harness isn't a simple tool - it's a bunch of components working together to give the best DX for testing JS code with native modules. Maintaining all that as a solo dev isn't easy, so I tried offloading some work by using Jest's CLI to run Harness… and it worked!

We're hosting a livestream today, with a special focus on React Native Harness! Expect insider insights on how it all works and sneak peeks at what's coming next.

🗓️ Thu 16, 5 PM CEST
See you there!

🎉 Introducing React Native Harness - a lightweight framework for testing native modules directly on device or emulator.

Write tests in a Jest-like syntax, run them in a real React Native runtime, and verify native behavior without mocks.

Are you using the Performance API in React Native? If yes, I'm pretty sure you've wished a bunch of times that you could check out measures like you do in Chrome DevTools. What if I told you Rozenite is about to bring you that same vibe? Hot or not?

Yesterday, the community requested server-side event support for Rozenite's Network Activity. I said I'd look into it… but somehow ended up pushing a branch with the feature almost done. Whoops! 🙈

The Rozenite plugin family is growing, so I created a plugin directory!

It includes both official plugins and community ones like rozenite-preview.

Best part? You can add your own by opening a quick pull request on the Rozenite repo.

Just found out I'll be speaking at React Universe Conf!

Rozenite's been out for a while, but in this talk, I'll dive deeper into how it works under the hood - how I hooked into DevTools without forking anything, and how you can build your own plugins too.

Hope to see you there!

New week, new feature! Struggling to understand what's going on in your WebSocket connection? Fear not! Thanks to Rozenite, you'll soon be able to inspect WebSocket traffic and review each message one by one - whether it's text, binary, or JSON. Coming soon 🔥

Bronze trophy unlocked: 100 stars collected!
It's not platinum (yet), but every legend starts somewhere 😉

Rozenite's Network Activity plugin got a major overhaul yesterday! The new UI and improved functionality make it much more convenient to use. You can now inspect request bodies and responses with an interactive JSON viewer 🚀

Rozenite - a plugin framework for React Native DevTools - is now live in alpha! 🎉

What started as a hacky PoC is now something you can use in real projects.

Still lots to come: better network monitor, Redux DevTools, Re.Pack support & more 💪

Missing memoization where it matters most?
Let’s fix that.

Join us for Part 2 of our React Native JavaScript perfomance deep dive - debounce, selectors, state shape & more.

📅 Apr 29 • 6PM CET
🎙️ @grabbou.com + me
🎟️ streamyard.com/watch/pnM9CY...

Your React Native application slowed down? We are here to help you! Join our walkthrough of Callstack's 2025 Optimization Guide (Part 1). You will have the opportunity to ask questions and have them answered for free, without any hidden catches.

streamyard.com/watch/VW8Ufy...

Meet Aurora - my personal sidekick for making the best of React Native projects 🌟

Me and the boys on our way to spread performance on underperforming tech projects 🚀

Stuck on a train in the middle of nowhere with no electricity. Kraków doesn’t want to let me go that easily. 😩