Re^4: "Accessors break encapsulation"

If your classes do substantial calculations, it's useful to test the private methods that do the sub-calculations.

Otherwise, you'll probably end up doing more work to manage all the code coverage cases. That is, you'll need to do the same code coverage, but you'll have to reason out how to get to each submethod, and ensure you pass it the right parameters to ensure all of it's children get called.

I'd just as soon call all the children directly, with valid, invalid, likely, and not so likely datasets, and ensure that all cases are handled correctly. If I know the sub-methods do their jobs, then testing the API becomes more of an excercise in confirming the behaviour of the API against the final set of business requirements, versus a frantic search for coding errors.

If you only test the API, you also run the risk of your subroutines containing hidden flaws that cancel each other out. If you try to re-use or refactor such flawed code, you'll be in for nasty surprises later on...

But then again, testing is a lot of work in general, and if you refactor the internal methods, updating the test suite each time is a real pain.
--
AC

Comment on Re^4: "Accessors break encapsulation"

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Re^5: "Accessors break encapsulation" by adrianh (Chancellor) on Jul 21, 2005 at 13:06 UTC
Otherwise, you'll probably end up doing more work to manage all the code coverage cases. That is, you'll need to do the same code coverage, but you'll have to reason out how to get to each submethod, and ensure you pass it the right parameters to ensure all of it's children get called. I find that this is rarely a problem in real world usage. This is probably a side effect of doing TDD. If I factor out a private method from a public method then the coverage of my test suite isn't going to change, and if I change my private method I'll always write a test first. To put it another way, if you aren't exercising all of the code in your private methods why did you need to write them in the first place?	[reply]
Re^6: "Accessors break encapsulation" by tlm (Prior) on Jul 21, 2005 at 13:16 UTC
adrianh, have you found some good material on TDD in Perl? I'm finding TDD, so far, only slightly less painful than debugging :-) . (Though I just received Kent Beck's book today, so maybe I'll pick up some wisdom there.) the lowliest monk	[reply]
Re^7: "Accessors break encapsulation" by simonm (Vicar) on Jul 21, 2005 at 15:44 UTC
If you haven't already, check out the TDD section in theDamian's article on Perl Best Practices.	[reply]
Re^7: "Accessors break encapsulation" by adrianh (Chancellor) on Jul 21, 2005 at 16:08 UTC
adrianh, have you found some good material on TDD in Perl? I'm finding TDD, so far, only slightly less painful than debugging :-) . (Though I just received Kent Beck's book today, so maybe I'll pick up some wisdom there.) There's not a huge amount available specifically on developing perl in a TDD manner. There's Rob Nagler's Extreme Perl, Peter Scott talks about it a little in Perl Medic and I believe that there's a bit on TDD in TheDamian's new book. But really there is nothing language-specific about TDD so I'd recommend reading Kent's book and taking it from there.	[reply]
Re^8: "Accessors break encapsulation" ("TDD") by tye (Sage) on Jul 21, 2005 at 21:25 UTC
Re^7: "Accessors break encapsulation" by jplindstrom (Monsignor) on Jul 21, 2005 at 20:13 UTC
You surely will. It's an excellent book! IIRC, it's one of those books with an actually ejoyable foreword that leaves you eager to continue reading. That itself is rare. /J	[reply]