From: Avdi Grimm <avdi@...>
Date: 2008-08-16T05:48:49+09:00
Subject: Re: BDD and TDD - What are they for?

On Fri, Aug 15, 2008 at 4:35 PM, Shadowfirebird
<shadowfirebird@gmail.com> wrote:
> I agree that the overhead is extra development time.

After doing TDD/BDD for, oh, five years or so, I'm convinced that the
"it takes longer" argument is a red herring.  It may be true when
you're first learning TDD and it takes you awhile to work out how to
properly test something.  But I've found that once I internalized
testing my coding velocity actually *increased*.  And more
importantly, it became much steadier.  Non-TDD projects are often
marked by a very fast initial ramp-up, then velocity starts to
decline, and then eventually they hit a wall where every change seems
to take 2-5 times as long as it should because of all the unintended
consequences.  TDD projects, by contrast, retain about the same speed
from start to finish.  Write test; watch test fail; make test pass;
refactor; repeat - it's a rhythm that stays constant no matter how
large the codebase.

I've also found that for me, personally, TDD reduces my initial
startup time.  In the past I used to spend a lot of time trying to
dream up the "right" object model to fit the project, and I'd have a
hard time actually figuring out where to dig in and start coding.  And
then when I did dig in for awhile, it would suddenly occur to me that
I'd failed to account for something basic and I'd realize I needed to
re-tool my design.  And of course the subsequent refactoring would be
prone to breakage because I had no regression tests.

When I'm doing TDD, all I have to think about to get started is the
simplest possible unit of concrete, testable functionality.  I make
that work the simplest possible way, and then move on to the next
simplest case.  As soon as I find myself duplicating code I refactor.
Out of this rhythm the "right" design emerges, a piece at a time - as
it is needed.  And there's no wasted time at the beginning trying to
figure out how to architect for the future.

Which is all to say why I find any project over, say, a hundred lines
of code actually goes *slower* without TDD/BDD.

-- 
Avdi

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