Rubyist and maker of things Staff Engineer @ Shopify 🛍️
Joined March 2015
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📢 Undercover gem v0.8.5 just shipped, featuring:
- new --format=json CLI option, which the Claude Code skill likes more than the default text format
- small fix for Ruby 4 compat
Currently working with two Claude Code's on a plugin that sets up and effectively uses undercover feedback loops.
Claude A is developing the skill. Claude B is a mock project that uses it with --plugin dir. It's been a struggle!
Does this mean we need a skill-writing skill?
Undercover 0.8.4 just dropped with an important bugfix to coverage reported for branched statements spanning multiple lines ✨
github.com/grodowski/underco…
"Absolutely essential for ensuring our AI agent-written PRs have the coverage we require." This is why I build tools, thanks for the shoutout @jaytennier
bsky.app/profile/jaytennier.…
Jan Grodowski retweeted
Written by yours truly! 🙇♀️
Give it a read and let me know what you think! #ruby #rubyonrails
🎩 New Ruby Magic: Create a Markdown Editor in Ruby on Rails
blog.appsignal.com/2025/12/1…
Just pushed pronto-undercover 0.4.0 to RubyGems! 🎉 ICYMI, it's a great way to integrate undercover with any SCM and any CI workflow and now it supports latest undercover again
Sponsoring @shortrubynews this week again, with updated messaging.
It's now easier than ever to produce thousands lines of code at speeds that make automatic review needed even more.
Undercover guides your coding agent to write complete and higher quality tests.
2025 has brought significant development to both Undercover CI and the undercover gem currently at 0.8.0. Thanks for the feedback and please keep it coming. Here are a few noteworthy changes 🧵
Dedicated SimpleCov::Formatter::Undercover.
:nocov: syntax support is fixed, and SimpleCov's add_filter now respects files outside of test coverage reports
Better relative path support allows running undercover in subdirectories and subprojects of monorepos.
More configs!🛠️
Ability to skip builds on specific branches via regex.
GitHub status modes: choose between "failure" ❌ to fail builds with coverage warnings (default), or "neutral" 🟡 to just get coverage annotations without failing the parent build status.
So glad we have a lively Ruby community in this corner of Europe 😇 @hschnedlitz was a fantastic host and MC *and* prepared the super fun quiz. Thank you for the hard work!
guess who’s taking over this account tonight! 👀😂
We’re now kicking off the summer edition of 🌸Vienna.rb 🌸 with @hanaharencar telling us about shipping thousands of commits daily in GitHub’s Rails monolith 🚀
EMRNDPD is email-marketing-release-notes-driven-product-design: write them first addressing your customers, but do not hit send. Now you know what needs to be done.
Jan Grodowski retweeted
Shopify, GitHub, Gitlab, Instacart, Intercom, Square, Coinbase, Figma, Chime, Cisco, and for example, Y Combinator's own software. Ruby and Ruby on Rails are doing pretty awesome!
Putting Cursor and Copilot to the test for this year's advent of code. After day 3, we are ~somewhat safe!
- AI won't always pick all the edge cases, "solve this" as a prompt is not enough (lol)
- the code is not always idiomatic
- but generally: times are changing! 🤯
Jan Grodowski retweeted
Yesterday was an incredible day for our merchants and for Shopify:
* Merchants drove a record-breaking $5 billion Black Friday in sales (GMV)
* Peak sales / minute for yesterday = $4.6 million
* Shopify's egress processed more than 173B requests
* Peak requests per minute was at 284 million on edge, with more than 80 million on app servers pushing 12TB a minute
* 45 million peak database queries per second, peak database writes was 7.6 million per second
* We rely on Kafka. At peak we hit 66 million messages per second
Let's keep going 🔥
Jan Grodowski retweeted
Oh hey is that our website looking so new and fresh? Looks like something is coming 👀
ruby.wien