You express intent much more clearly with explicit types, and there are lots of other benefits. For example, you’ll get much better auto-completion of method parameters in your IDE.

@Andrew

I suppose I’m (over)reacting to some styles of TDD that I’ve seen — and that I’ve done myself. I think there’s a worst-case combination with some interpretations of DTSTTCPW that leads to code that’s all implementation.

To me, this is a case of applying some domain knowledge and coming up with the conclusion ‘I need an address now’ - so you are going to need it. YAGNI would be applied however if you guessed what methods you needed for you address ahead of time - for example if you don’t need a post code now, don’t add it just in case. I also tend to use objects instead of built in types no matter how small - firstly to aid understanding and secondly to encapsulate any business knowledge where it belongs.

I like this a lot - a really succinct way of describing why so much code is such hard work to understand.

And a strong second for Abelson and Sussman. Teaching programming via functional abstraction now seems prescient…