Episode 3 of the 2026 Edition - The longest Kotlin night of the year

The longest day of the year is comming and let's another Kotlin meetup. This time we geather at N26!

⚠️⚠️⚠️ Due to a venue policy please submit the following form for additional details. Without it, you won't be allowed inside the venue:

https://forms.gle/XjqVXkD3FARCM6jA8

Line-Up:

👉 TestBalloon: Kotlin testing is easier (and more fun) than you think
by Oliver Okrongli

You want an easier way to write tests? Parameterize tests in plain Kotlin? Reuse a series of tests? Easily extend own your test setup? Have first-class support on all platforms? All without struggling with a huge framework API? TestBalloon is a new test framework that brings the power of Kotlin to your test setup. With a small-surface API, a hierarchical test structure and an extensible DSL, TestBalloon makes Kotlin testing easy, even at scale. Oliver, the author of TestBalloon, will show testing patterns and strategies and lots of practical examples, ranging from simple unit tests with less boilerplate to advanced testing with coroutines and generated data. This talk is based on insights first presented at KotlinConf 2026 in Munich. At the end of this talk, you’ll be able to firmly the answer the question: "How can I master Kotlin testing with ease, and make my team release with joy and confidence, every time?"

👉 One Topic to Rule 'Em All
by Yonatan Karp-Rudin

Kafka delivered every event exactly once, in order, and lost nothing. So what broke? This talk follows that question into the gap most event-driven systems leave open: what actually guarantees the order your domain depends on, and what quietly doesn't. We start from a real log line, find the crack in an architecture that looks clean and ships fast, and rule out the fix everyone reaches for first. The cure turns out to be one sentence of domain thinking plus one line of config, though the Schema Registry will fight you on the way there. A live demo runs the bug and the fix back to back: same load, same hero, one change. If you build with Kafka, you have probably shipped a version of this bug. You will leave able to spot it and fix it before it pages someone.

👉 TBD

Speaker Bios:
🗣 Oliver Okrongli

Oliver has been shaping and creating software from backend to frontends. He is the author of TestBalloon, a next-generation Kotlin test framework. Before, he has helped to maintain Kotest, and contributed to several libraries of the Kotlin ecosystem as well as the Kotlin compiler. Can be found on GitHub (OliverO2) and the kotlinlang Slack (Oliver O).
When not developing, he is most probably in deep talks, dancing, snowboarding or F18 catamaran sailing whenever he gets a chance.

🗣 Yonatan Karp-Rudin

Yonatan Karp-Rudin is a Staff Engineer at Billie, building event-driven systems in Kotlin and Spring Boot. Off the clock, he plays with AI agents and builds random tooling, trying to hand off as much of his own workflow to a machine as he can. The rest of the time he's brewing mead or deep in a video game.

🗣 TBD