Comment on Testing on High: Bottom-up versus Top-down Test-driven Development by Merlyn Albery-Speyer

Sun, 25 Nov 2007 01:11:04 -0800

Good post, Ryan. I do find the difference in outside-in and inside-out philosophies interesting. I recommend reading from xUnit Test Patterns on the topic if you haven't already.

TDD from the outside-in is my preference, but I can't quite express why it feels 'the right way' to me.

I would argue that nothing is working until it's working end-to-end. Is outside-in really slower as you suggest?

Unfortunately, I don't always start at the highest level of abstraction. I'm limited to the highest level that can provide me with rapid feedback otherwise development quickly stops being TDD in my opinion. So, I pretty much always start just below the user interface layer. Does that make me some sort of mutant middle-in TDDer then?