Errors caught by WBT, but not BBT and vice versa

Question

Hi Folks,

Can you think of one type of error that might be found using White-Box testing, and one type using Black-Box testing. i.e. an error that would be found by one and not the other.

For WBT there would null else statements, but what would you catch with BBT and not WBT???

BTW this question is just based on my own personal study - I'm not getting free marks out of this!!!!

Thanks,

Answer 1

The advantage of white box testing and the extra errors it finds are entirely due to testing all cases. If you don't know how something is implemented you can never be sure you have tested it for every input in every state because the state is internal.

Of course if you have coverage tools this can be avoided but unless you have the code it can be very difficult to work out what might test the 8.3% of lines you're missing.

I can't think of something black box testing will find that white box testing won't but I will say that it tends to be much more useful because it allows people to tinker with or completely rewrite the box without having to touch the test case. Important because if the test is modified you lose some ability to regression test.