Skip to content
Home » Test Driven Design: at its best when it’s outside in

Test Driven Design: at its best when it’s outside in

I’ve been playing around with rust for a few months – on and off. And I came to a halt without realising it and couldn’t get restarted.

Why?

Because I’d come to the hard bit – the business logic. What was this thing actually going to do and how was it going to do it?

And the truth was, I didn’t know. So instead of writing more code, I just stopped.

I’ve been trying to find an excuse for doing a TDD project. Because I have some experience, I know the one thing I don’t want to do is write any more code than I need to. I want to write just the right amount of code for my project to do what it needs to do.

So imagine my surprise when – on reading Kent Beck’s Test Driven Development: By Example – that I had everything I needed already.

I thought I might join an existing open-source project, or refactor one of the ones I’d worked on before. But in my nascent rust project I had the start – what I needed now was the design.

So I wrote a test or two and it felt good. But what next? At that point, I realised intrinsically that I need to go outside-in. Rather than building tests at the heart of the logic, I needed to build tests at the outside interfaces.

This article does a much better job of explaining it than I can. Suffice it to say, I’m unstuck. I’m thinking, I’m writing code. But also, I’m designing, and it feels AMAZING.





Discover more from Richard Bown

Subscribe now to keep reading and get access to the full archive.

Continue reading