Appsterdam's weekly Saturday morning co-working session, this week at The Coffee Room on Ferdinand Bolstraat. Bring a laptop and whatever you are working on; there is no programme, no speaker…
Kotlin Meetup: Contract-Based Testing & Kotlin Contracts
Wednesday 4 November 2026·5:30pm·Xebia Netherlands
Date & Time
Wednesday 4 November 2026
5:30pm – 9:00pm
Price
Free
N-
Organiser
NLKUG - Dutch Kotlin User Group
Xebia NetherlandsOpen in Google Maps
About this event
Two talks on contracts, from opposite ends: the integration kind and the compiler kind.
Willem Veelenturf and Jerre van Veluw of Flock.community walk through Flock's architecture and Wirespec, their tool that turns an API contract into type-safe code on both sides of an integration, then build contract-based integration tests from scratch live with Kotest. Alejandro Serrano Mena of JetBrains follows on in-place, return and flow contracts in Kotlin, what the compiler does with them, and how they are turning into new language features.
Free, at Xebia on Wibautstraat. Doors 17:45 with food and drinks, talks at 18:40 and 19:40, drinks from 20:30. Hosted by the Dutch Kotlin User Group with Flock Community and Sourcelabs.
Why go: a JetBrains engineer explaining contracts in person, and a live-coded testing demo you can copy on Monday. Best for JVM and Kotlin developers and anyone maintaining API integrations.
Speakers
WV
Willem Veelenturf
Software Engineer and co-founder, Flock.community
JV
Jerre van Veluw
Software Engineer, creator of Wirespec, Flock.community
AS
Alejandro Serrano Mena
Researcher, JetBrains
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