Re: Bad test functions in Test::Exception

Subject: Bad test functions in Test::Exception
From: Nadim Khemir <nadim@xxxxxxxxxx>
Date: Tue, 30 Jan 2007 18:17:38 +0100

}I like Test::Exception, it's a very fundamental test module with 
}Text::NoWarning, Test::Deep and other goodies. Still, I believe some of the 
}functions made available should not be there at all. 

Not everyone uses Perl the way you do.  Different people have needs for 
different functions.  Saying "I don't use this and can't think of a reason 
for it, so get rid of it" makes a lot of assumptions, many of which 
probably aren't true.
 
}  # Check that something died
}  dies_ok { $foo->method1 } 'expecting to die';
}
}Am I the only one who got this to pass, to find out later that what cause the 
}error had nothing to do with the message I displayed.

No, you're not - but shunning all possible uses of dies_ok becasue you 
didn't write a test as complete as you could have isn't the fault of 
Test::Exception.  

How about code that dies with an object?  dies_ok lets you inspect the 
object in $@, whereas throws_ok only lets you see if it's part of a class.  
What if you want to see if $@ meets multiple criteria?  There's plenty of 
valid cases where throws_ok just isn't enough.

And finally, what if I truly don't care why something dies, just that it 
did?  Why should I be penalized for writing *any* test?

}  # Check that something did not die
}  lives_ok { $foo->method2 } 'expecting to live';
}
}Is the above realy a test? Ok but testing what? why wouldn't we wrap all our 
}test in lives_ok? No, I don't think lives_ok makes any sense. I'd be very 
}happy to see real examples of lives_ok that add anything to a test suite.

I have this in the production code where I work, and it's very necessary.  
If you have an interface that requires you to die on invalid input, it's a 
life-saver, especially during debugging.  While I won't paste code from my 
work here, consider your exact case:

}  # Check that a test runs without an exception
}  lives_and { is $foo->method, 42 } 'method is 42';
}Isn't this equivalent to is($foo->method, 42 , 'method is 42') ?

No!  If the latter fails, the test stops where it is, and no further tests 
proceed.  If the former fails, it's another 'nok' to investigate, but the 
rest of your tests have an opportunity to run.

}I postulate that Test::Exception would be even better if we removed the bad 
}guys.

And I postulate that you're not willing to change all the code in the 
world that uses them, for reasons I've stated above and more.

Besides which, if you remove those functions, people will either stop 
using the module (and possibly stop testing as much) or will invoke the 
laziness part of Perl and do this:

  throws_ok { $foo->method } qr//, 'method dies'

People have personal and organizational code standards to meet, and that's 
to be expected.  Be sure to update yours to the things you've mentioned.  
TIMTOWTDI rules here, though, and PBP isn't a rulebook - it's a set of 
guidelines that work for Damian.  Other people use them to varying 
degrees, and P::C even implements them, but at some point, people are on 
their own.

-Pete K
-- 
Pete Krawczyk
  perl at bsod dot net