Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!uunet!hsi!stpstn!cox
From: cox@stpstn.UUCP (Brad Cox)
Newsgroups: comp.software-eng
Subject: Re: assert() (was Re: "Program Proving")
Message-ID: <4468@stpstn.UUCP>
Date: 9 Apr 90 16:34:56 GMT
References: <1990Mar17.063012.24979@agate.berkeley.edu> <4389@stpstn.UUCP> <4559@pegasus.ATT.COM> <47859@lanl.gov>
Reply-To: cox@stpstn.UUCP (Brad Cox)
Organization: Stepstone
Lines: 34

In article <47859@lanl.gov> u096000@lanl.gov (Roger A. Cole) writes:
>Various articles have discussed the value of assert() in producing quality
>software.  As a long-time programmer with a relatively recent conversion
>to C, I am intrigued.  I am also, in keeping with observations in various
>articles, ignorant about assert().  (So are other programmers at my site.)

Although this paper doesn't mention assert() by name, you might start
with my paper, now being reviewed, for the Novembmer 1990 issue of
IEEE Software Magazine, "Planning the Software Industrial Revolution;
The Impact of OO Technologies".

One section of this paper, "Technologies: Programming Languages are not
sufficient", derives from Stepstone's experiences in building and supporting
commercial libraries of reusable object-oriented code libraries.  Since a
commercial operation is continually faced with extending code that already
has large numbers of clients, porting code to new platforms, and repairing 
defects, we were continually plagued by the problem of verifying that old 
client interfaces were not being changed while independently verifying that 
the new changes in fact complied to the new specification.

The system that we presently use to do this is entirely based on programmer
supplied assert() statements, of two distinct kinds: (1) structural (white
box) testing, with assert()s embedded inside the product, and (2) functional
(black box) testing, with assert()s contained in independent files that I
call Gauges, by analogy with the gauges that played such an important part
in Eli Whitney and his successors' vision of interchangeable parts.  The
article sketches a more ambitious system that deploys a knowledge 
reprersentation language as a specification/testing language.

If you're interested, send me a mailing address and I'll mail a copy.
I have no additional written information about how we use asserts() at this
point. However I'll be teaching this approach to specification/testing as 
part of a Objective-C course at the UC Santa Clara Techmart Extension the
last week of July.