DDD eXchange 2010: Gojko Adzic on DDD, TDD, BDD

The three amigos@gojkoadzic

Effective models require a bigger picture

… but KISS and YAGNI say don't... avoid BDUF

… feature injection gives us right-size chunks

Things can blow up during modelling...

… but domain experts often can't decide on scope

...collaborative specifications cause things

to blow up quicker

DDD advocates a ubiquitous language...

… but it's very hard to ensure consistency

… evolve with specification workshops,

enforce with tests

Domain experts don't really understand low level

stuff

.... but where do we stop working with them?

...BDD outside in boundaries

...TDD emergent design to flesh out details

Emergent design leads to too much inconsistency

… especially on big teams and across boundaries

… use DDD building block patterns as guidelines

Effective iterative design requires effective regression testing

… but unit tests are bound to a particular design

… business oriented specifications do not

change

We need to capture our models and what they

mean

… but code is too low level and UML gets old very quickly...

… live specification can explain our models and

dynamics

Emergent design advocates constant

refactoring

… but in larger teams, refactoring cross cutting concerns can cause a ton of issues

… bounded contexts help us coordinate changes

Recipe for success

Use strategic design to decide what to build Use feature injection to get the scope Evolve a ubiquitous language with specification

workshops Establish guidelines with collaborative high-

level domain design TDD design below, respecting DDD guidelines Use context mapping to facilitate cross team

collaboration

Questions?

http://gojko.net

@gojkoadzic

gojko@gojko.com