19 November 2005

Testing: disciplin, attitude and intuition (2/3)


I ran across a test today that I found interesting. The tested class was one of our association containers (see previous blog entries), a List to be more precise. A list can contain several times the same element.

Believe it or not, I am not sure that writing the tests for that class I would have thought to include that kind of specificity. I am glad I didn't develop the test case for that class,... because the developer that did, did it right. He had tests that included that specificity.

I am not sure that the first implementations of the class needed that kind of test, but surely the modifications I introduced afterward failed because of that blessed test!

I think the main difference between our 2 state of minds is that I tended to do white-box testing whereas the other developer did black-box testing. That's a very different state of mind:
  • when you do white-box testing, you know what could go wrong and you test it
  • when you do black-box testing, you define what you expect but since you have no idea of the implementation, you try to expect most of it. So you add the same element twice in the List. You dont want to guess what could go wrong, you just want to test what is ok for you
To that extent, testing is also a matter of attitude. Having the "tester" hat is quite different to having the "developer" hat. Switching between the 2 may not be so easy, hence the need for disciplin mentioned in the previous entry.

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