From: Robert Klemme <bob.news@...>
Date: 2004-07-29T18:46:44+09:00
Subject: Re: Test-First vs. Bottom-Up


"Peter Hickman" <peter@semantico.com> schrieb im Newsbeitrag
news:4107ADE9.8080906@semantico.com...
> tdd or 'test first' has nothing to do with 'bottom up' or 'top down',
> you can do ttd with either. tdd has a lot to do with how you write the
> code, ie write the tests before the code, get the tests to pass and then
> write more tests / code. 'top down' or 'bottom  up' is more about the
> order that you write / develop the code.
>
> if you start your design top down you can use tdd to drive the coding.
> remember you can fake the lower level elements as stubs until you get
> round to coding them.
>
> if you start bottom up you can use tdd in the same way except that you
> don't have stubs to fake the lower levels you have harnesses to fake the
> higher levels.
>
> there is absolutly no conflict between tdd and 'top down' / 'bottom up'
>
> remember 'top down' and 'bottom up' are DESIGN methodologies and tdd is
> test driven DEVELOPMENT (to quote from the spine of beck's book on the
> subject).

I was going to say the same.  Two additional remarks: as you mention
implicitely, using bottom-up with tdd might be a bit easier / faster
because you save yourself all those lower level stubs that you need with
top-down and tdd.

The choice between top-down and bottom-up very much depends on the type of
software that you are creating: roughly speaking bottom-up usually results
in more reuse and is better suited to libraries while top-down is better
for application development because breaking down complex tasks into
smaller tasks is the simplest way to get from requirements / use cases
down to software.  Of course this is rather a rule of thump, typical
applications contain parts that are rather library-style and other parts
that are rather application-style.  So you might end up using both.

Kind regards

    robert