Re: What Constitutes a Good Test?

[Andy Lester]

Testing is all about checking for the stuff that shouldn't go wrong, 
but might, as well as defining what your code should do, and verifying 
it.  It's all about writing down the bones of what the code is supposed 
to do, and then making sure you didn't break it somewhere along the 
line, and in the case of module distros, that it works on platforms 
other than yours.

Here's a crash course in the whys: 
http://petdance.com/perl/automated-testing/  I'll also be giving a 
session on automated testing at OSCON 2003, which will be more 
example-heavy and less about philosophy.

Here's another: any core module in the Perl distro, or any particularly 
well-tested module on the CPAN.

Accumulate your tests over time.  Let 'em build up like so many 
soldiers against bugs.  Quantity is almost as important as quality.

Test the edges.  How is your module supposed to handle an invalid parm 
to the constructor?  Define it, document it, then test that that 
happens.  How about specifying a buffer size of 0?  etc etc.

Basically, if the docs say your module is supposed to do something, 
then the tests should test exactly that.

Remember that there are no stupid tests.  The following

        $foo->set_bar( 12 );
        is( $foo->get_bar, 12, "Accessor works" );
is perfectly valid as a test, and should be done for every accessor you 
have.  "But it's an accessor!  How can that fail?"  I don't know, but 
when it does, you want to know why.

I'd be glad to take a look at your module.  It's a lot easier to poke 
at specifics.

xox,
Andy
--
Andy Lester
[EMAIL PROTECTED], AIM:petdance
http://petdance.com/ http://use.perl.org/~petdance/