From: Jim Weirich <jweirich@...>
Date: 2003-05-17T09:00:14+09:00
Subject: Re: Test::Unit sequencing

On Fri, 2003-05-16 at 13:49, Austin Ziegler wrote:
> On Sat, 17 May 2003 00:27:33 +0900, Michael Campbell wrote:
> > I know this is wrought with exceptions, but a very crude rule of
> > thumb is that if your code is not easily testable, it's probably
> > poorly designed, too tightly coupled, not cohesive enough, too
> > big, etc.; in other words, due for a re-think.
> 
> I would strongly disagree with this. 

Really?  I would agree that it is difficult to add unit tests to an
existing design (I have plenty of examples of that!).  But if you are
doing a design in a test-first manner (using TDD), I find it difficult
to imagine something that would not yield itself to good unit test
coverage.  

The counter example is always GUI code, but I've found that even in the
few projects I've done requiring a lot of GUI work, a significant
portion is still unit testable.  The GUI work becomse a thin layer on
top of the business logic ... a much thinner layer than I would have
imagined before doing TDD.

> There are some things that
> aren't really able to be broken into clean units for testing. Two of
> the projects I'm working on right now are difficult to unit test.
> Both of them are involved with creating and manipulating documents
> that are intended to be dealt with by other programs. In general,
> the documents have to be completely correct, or they aren't valid at
> all.

Fascinating!  But I'm still not sure I understand /why/ unit tests are
hard.  Could you elaborate on this.  Perhaps even give a mini-example. 
Thanks.

-- 
-- Jim Weirich     jweirich@one.net    http://w3.one.net/~jweirich
---------------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)