From: Robert Klemme <bob.news@...>
Date: 2005-10-17T21:46:57+09:00
Subject: Re: Nifty Proxy Object for Testing

Brian Schr�der wrote:
> Hello Group,
>
> I had an idea for a testing method I wanted to share. I develop a c
> extension that efficently implements a priority queue. An inefficent
> pure ruby reference implementation can easily be written, so I have a
> reference implementation and my c implementation and want to assure
> that they behave the same. I achieve this by using a proxy object in
> my tests that does all actions on both implementations and asserts
> that return values and thrown exceptions are equal.
>
> That allows for double testing. I assure that my normal unit tests
> work and additionally for each action it is tested that the right
> thing is returned. Furthermore the teardown method now tests that the
> actions have resulted in the same state in both implementations.

Maybe I didn't understand this correctly but if you have "normal" unit
tests already, why then do you need a result comparison?  I mean, if
instances of both classes pass the unit test results should be the same or
at least compatible.

Alternatively you could use the Ruby implementation to yield expected
values that are compared with the C version, but that has the same problem
as a comparison only test: you won't catch algorithmic flaws that you made
(if you developed both it's likely that both exhibit the same erroneous
behavior which you won't catch with the comparison approach).

Kind regards

    robert