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Staff software engineer, maker, generalist.
* 11+ years in professional software…
* 11+ years in professional software…
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1026 Follower:innen
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👨💻 Jan Grodowski hat dies gepostetI wrote here a few posts ago how coding agents write features and tests with increasing ease and pace these days. That's the new default. The bottleneck for teams running production apps has shifted from making code changes to reviewing and owning them. The same number of people look through more and more diffs per day, and it's on them to ensure quality doesn't decline across the board. But agents have blind spots. They test until the happy path works and then move on. So I ran a weekend experiment: same coding task, complex enough to be realistic, given to Opus and Sonnet with and without an active test coverage feedback loop powered by undercover. Yes, I built the same app four times, so you don't have to. All four builds passed a blind test suite eventually, but the paths there were different. The plain runs: - Finished at 65-75% branch coverage - Contained more (and more severe) functional bugs - Required more fix rounds The skilled runs: - Produced fewer, surface-level bugs - Ended at a healthier test-to-implementation LOC ratio - Removed dead code actively instead of leaving it in - Took more turns and cost ~2x more to complete The insight: current models know how to test well, but an active coverage constraint with the right scope doesn't just produce higher coverage numbers to make you feel good, it influences the correctness and quality as code is being produced. Full writeup with data and examples in the comments.
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👨💻 Jan Grodowski hat dies repostet👨💻 Jan Grodowski hat dies repostet"Absolutely essential for ensuring our AI agent-written PRs have the coverage we require." Jay Tennier of Rainforest QA https://lnkd.in/dqi7KTr8
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👨💻 Jan Grodowski hat dies geteiltBeen running ads for Undercover with Ruby Weekly and Short Ruby Newsletter over the last few weeks with a simple message: your 90% coverage is hiding untested methods, especially in AI-generated code changes. Undercover catches what coverage percentages miss, right in your PRs and in your local workflow. If you saw the ads, I'd love to hear whether the message landed!👨💻 Jan Grodowski hat dies geteiltIf you're still thinking the Ruby ecosystem is slowing down, this new edition of Short Ruby Newsletter will change your mind. This edition is sponsored by UndercoverCI - the Ruby coverage toolkit ready for the vibe coding era - visit https://undercover-ci.com Some highlights: 🚀 New Launches Marco Roth launched charm-ruby.dev bringing elegant terminal experiences to Ruby Vladimir Dementyev announced the second version of Layered Design for Ruby on Rails Applications Marc Köhlbrugge launched rclown and Sessy for object storage backups and email observability David Backeus launched lovingruby.com with 365 reasons to love Ruby 📅 Events & CFPs BalticRuby extended CFP until end of January Belfast RubyFest 2026 happening on 11 February Ruby Kaigi CFP has one more week Brighton Ruby 2026 CFP is now open 👉 Ruby Updates Rafael Mendonça França announced Rails 8.1.2 Yukihiro Matz shared that mruby 4.0 is coming Kevin Newton published exreg: a Ruby Regular Expression Engine André Arko announced a new release for rv, an extremely fast Ruby version and gem manager As always, there are more links to newsletters, videos, podcasts, and articles inside. This edition was possible with the great help of Vladut Cosmin who did the entire content editing! Read the full newsletter for free at https://lnkd.in/dDripvS3
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👨💻 Jan Grodowski hat dies repostet👨💻 Jan Grodowski hat dies repostetSponsoring Short Ruby 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. How do you like this angle? Go check out https://lnkd.in/eaJ9tTmD 🚀
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👨💻 Jan Grodowski hat dies geteiltUndercover gem & app in push mode this year 👀🚀👨💻 Jan Grodowski hat dies geteilt2025 has brought new development to both Undercover CI and the undercover Ruby gem currently at version 0.8.0. Thank you for all the feedback that led to these changes and please keep it coming! Configuration for GitHub status failure modes: choose between "failure" ❌ to fail builds with coverage warnings (default), or "neutral" 🟡 to just receive PR annotations without failing the parent build status. Relative path support that allows running undercover in subdirectories of monorepos. Undercover CI now respects .undercover config files stored in your repos. Dedicated SimpleCov::Formatter::Undercover, with plans to sunset the LCOV formatter early next year. :nocov: syntax support is fixed, with tighter integration with SimpleCov for tracking files outside of test coverage reports (e.g. respecting add_filter). Ability to skip builds on specific branches, configured via regular expressions, to support your team's GitHub workflow. Dashboard UI with aggregated pull requests stats and timeline for your GitHub Organization. Private API to interact with code coverage checks from your CI build. Massive performance improvements for analysing large pull requests. New Pro pricing plan to accommodate large teams with thousands of PRs per month. All of these changes make Undercover ready to support Ruby teams with an actionable test coverage git workflow that's so much more than a vanity metric. With Undercover, you prevent real bugs, highlight misunderstandings about what's being tested in each PR and keep your test suite healthy over time. 📈
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👨💻 Jan Grodowski hat dies repostet👨💻 Jan Grodowski hat dies repostetSave the date! The next Vienna.rb is happening on the 5th of June! 🏖️ We have a fantastic program with incredible speakers and a surprise prepared. More details to follow soon!
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👨💻 Jan Grodowski hat dies geteiltAnother trip to Vienna it is! Can‘t wait to meet you there👨💻 Jan Grodowski hat dies geteiltMark your calendars! 📅 Vienna.rb #64 happens on June 5th. This time, our friends at PlanRadar are hosting us. We have a special guest, Hana Harencarova, coming all the way from Switzerland. Alexander Fiedler will be talking about what it's like to build software for building buildings with Ruby on Rails 🏗️ There'll also be the first-ever Vienna.rb Ruby Quiz - with awesome prizes to win! 🏆 Check it out! https://lnkd.in/dg_kQnqYVienna.rb #64 - Ruby Summer Meetup, Thu, Jun 5, 2025, 6:30 PM | MeetupVienna.rb #64 - Ruby Summer Meetup, Thu, Jun 5, 2025, 6:30 PM | Meetup
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👨💻 Jan Grodowski hat dies geteiltThanks for having me Vienna.rb, you were such a fantastic and engaged audience! Shoutout to Carmen Huidobro and Hans-Jörg Schnedlitz for creating yet another meetup with such welcoming atmosphere. 🚀 Can't wait for the next one!👨💻 Jan Grodowski hat dies geteiltLast week's Vienna.rb was incredible. We had great talks, a full house, and awesome vibes. Not to mention pizza! 🍕 That's all I really wanted when I decided to start organizing these Meetups. Connecting Rubyists, providing a space for people to have a good time, and bringing some much-needed visibility to the Ruby community in Vienna. I can't wait for the next one. A huge thank you to our speakers 👨💻 Jan Grodowski, Seth Horsley, Tony and Johannes Daxboeck! And, of course, thank you to our sponsors, Ruby Central, Inc., Fastly, and Platogo, for making Vienna.rb possible. P.S. I have some neat ideas for next-quarters Vienna.rb - stay tuned 😉
👨💻 Jan Grodowski hat auf einen Kommentar geantwortet
2 Monate
We have topics to try in Part 2 (once the weekly token limit resets 🙏)
👨💻 Jan Grodowski hat auf einen Kommentar geantwortet
2 Monate
Thanks for sharing your thoughts!
About the integration-style testing: my starter prompt asked for tests and Claude took it too literally, causing the generated tests to be quite sluggish: "Tests with Minitest + a GitSandbox helper (tmpdir + bare remote per test)". Worth removing and retrying.
On the meta-point about skills: it's interesting how much they add really w.r.t. the inherent knowledge of the underlying LLM. Undercover has too few occurrences in training data to be there, but other libs are picked up by default.
The "facts" the coverage failures surfaced could be generalised to rules like:
- test all failure paths (harder :D)
- don't leave out dead code
- don't rescue the same error twice
- run the program from the top-level executable to ensure it starts
LLMs should know these by now and yet they seem to work better when equipped with constraints.
👨💻 Jan Grodowski hat auf einen Kommentar geantwortet
2 Monate
Przemysław Mroczek the official frontend-design skill has been a game changer for building Rails UIs that have a solid starting UI/UX, it's pretty much always on since Bartek Kruszczynski recommended it to me :)
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiertHi All! Our team runs Shopify's global database service on YugabyteDB — a PostgreSQL-compatible, horizontally scalable distributed database that's fast becoming the system of truth for the entire business. We're looking for an experienced engineer to design, build, and operate a highly available control plane for our YugabyteDB clusters: one that keeps the database layer resilient and low-latency while engineering away the manual toil. This is distributed systems at global scale, where failure modes you usually only read about are real, and the blast radius reaches millions of merchants making their living on Shopify. If you're interested, please check out the role. Feel free to connect with Osama Mazahir Khosrow Ebrahimpour! We'd love to talk to you. https://lnkd.in/gAj2MmHhSenior Infrastructure Engineer - Database PlatformSenior Infrastructure Engineer - Database Platform
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiertLets gooo - 9 Mothers https://lnkd.in/gq4eizVe5 Companies to Watch From Y Combinator’s Spring Batch5 Companies to Watch From Y Combinator’s Spring Batch
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiertNo one: Can you be simultaneously #1 and #5 on HN?
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👨💻 Jan Grodowski hat darauf reagiertCheck out the story by Emilie Noel on what I've been up to in 2025. Involved a lot of hacking on MySQL to move Shopify's oversell protection off Redis, using SKIP LOCKED at Black Friday scale. https://lnkd.in/gFbtTsW2We replaced Redis with MySQL for inventory reservations—and it scaled (2026) - ShopifyWe replaced Redis with MySQL for inventory reservations—and it scaled (2026) - Shopify
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👨💻 Jan Grodowski hat darauf reagiertCouldn't be happier to see this. The Rails community has always prioritized programmer happiness and sustainable businesses. Even in 2026. Rails is very much alive.👨💻 Jan Grodowski hat darauf reagiertRuby on Rails has taken over NextJS 🚨 and Vercel is still just above Cloudflare n = 3,658 startups
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiertThe most dangerous thing about building with AI: a broken app and a working one look identical in the demo. I keep seeing non-technical founders ship apps that run perfectly until the first real user, then fall over in the same few places. Not carelessness. An AI coding agent has one goal: Making the code you asked for run. It quietly skips whatever isn't that. Four guardrails it skips by default: 1. Boundaries. It reaches into things you didn't ask it to touch to make a feature work. 2. Ownership. It writes code only it can read. Which means you don't really own your own app. 3. Failure paths. It builds the happy path. The "what happens when this fails" path is usually missing. 4. Architecture. When the model gets a vote on structure every session, coherence erodes unless a human holds the line. As Obie Fernandez put it: AI coding agents have made it impossible to pretend architecture doesn't matter. The through-line: the founder has to be the guardrail, because the model won't be. My test for whether you still are: you should be able to draw your whole app on a napkin at any moment. If you can't, the AI is steering. Written for founders building real businesses on AI-generated code: https://lnkd.in/dKvqbiTUThe guardrails non-technical founders skip when building with AI - Julian RubischThe guardrails non-technical founders skip when building with AI - Julian Rubisch
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiert78 commits and counting since the release of 1.16 last week! Can't wait to show all that's coming to RubyLLM 2.0.
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👨💻 Jan Grodowski hat darauf reagiert👨💻 Jan Grodowski hat darauf reagiertWe're hiring remote design engineers and product engineers in US, Canada (and EMEA). If you're looking for a role where focus is your most important resource (low-slack, low-meetings), reach out. https://lnkd.in/g3ptH9A2 https://lnkd.in/gzs7d2pi
Berufserfahrung und Ausbildung
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Shopify
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Bescheinigungen und Zertifikate
Kurse
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Building Mobile Applications (Harvard Extension School)
CS-E76
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Machine Learning - Stanford University (Coursera)
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Self-Driving Car Nanodegree (Udacity)
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Sprachen
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angielski
Verhandlungssicher
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niemiecki
Fließend
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polski
Muttersprache oder zweisprachig
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hiszpański
Grundkenntnisse
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