please also read my other articles. This form has proven many time faster to develop. The immutability is just a by-product — but also an extra benefit.

But the real benefit is that the behaviour is clearly expressed as types.

expressing behaviour isnt boilerplate.

I cannot go into every aspect of this Declarative Domain Paradigm in every article. And you cant make an informed comment if you dont give it a try yourself. Solar everybody who tried and contacted me, expressed that they found the same behaviour: It is coded much faster, all domains are expressible and especially testing TDD and BDD becomes trivial easy.