Romeu Moura

Romeu Moura

Reasoned Schemer

@malk_zameth · France


Endless conversation — with friends & compilers — on art, crafts, dialectic, paradigm jump, serendipity.


Domain Invariants & Property-Based Testing for the Masses

Domain invariants are all around you. In every business rule your domain expert ever tried to give you. You should use them to guide your design.

You should also be testing them! Not only an example representing them: but testing the invariant itself.

You can do them with property-based tests (PBTs). If you think you cannot do PBTs on legacy codebases (or outside FP) this talk should show you otherwise.

Let’s also use Property-based tests to reduce test-debt. Create smaller, fewer tests that: test more, are more readable & document the problem. Challenge your understanding of the domain and communication with domain experts.


Fight the Systemic Issues why your Code is Sad

Try to create a code you will not consider “legacy”.

I’ll play the role of your client and use around 20 techniques to make you fail.

You will fail.

We’ll then discuss what techniques I have used, how they happen in real life, how to fight them in your project.

All languages welcome. Bring your own laptop with your environment. We’ll split into small teams.

Mel Conway

Inventor, Educator, Author of “Conway's Law”

Eric Evans

Author of “Domain-Driven Design”

Rebecca Wirfs-Brock

Responsibility-Driven Design

Udi Dahan

Founder of NServiceBus

Prof. David West

Author of “Object Thinking”

Weronika Łabaj


Jimmy Nilsson

Author of “Applying DDD & Patterns”

Debasish Ghosh

Functional and Algebraic Domain Modeling

Nick Tune

Co-author of “Patterns, Principles and Practices of DDD”

Greg Young

Creator of CQRS

Alberto Brandolini

Inventor of “EventStorming”

Felienne Hermans

Author of "Grokking Computational Logic"

Robert Smallshire

Modeller of domains, systems and processes

Yves Lorphelin

Loves Chaos & Failures

Andra Sonea

Solutions Architect, Financial Services

Vaughn Vernon

Author, consultant, trainer

Arnaud Bailly

Event Sourcing, Functionally

Thomas Ploch

Infinite State Machine

Thomas Coopman


Stijn Volders


Scott Wlaschin

Creator of

Romeu Moura

Reasoned Schemer

Avraham Poupko

Technical leader

Jérémie Chassaing

Software Gardener

Paul Rayner

Leading DDD and BDD practitioner

Oana Juncu

Agile Business DJ

Nicole Rauch

Software Developer and Development Coach

Cyrille Martraire

Deliberate Designer

Michel Grootjans


Allard Buijze

Pragmatic modeller, creator of AxonFramework

Mathias Verraes

Student of Systems

Marijn Huizendveld

Nerd in a suit

Ken Power

Complexity Navigator

Edwin van Wijk

Software Architect

Yves Reynhout

The Journeylist

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