Black box vs White box Testing

manpreet Best Answer 2 years ago

Which type of testing would you say should be the emphasis (for testers/QAs), and why?

A quick set of definitions from wikipedia:

Black box testing

• takes an external perspective of the test object to derive test cases. These tests can be functional or non-functional, though usually functional. The test designer selects valid and invalid input and determines the correct output. There is no knowledge of the test object's internal structure.

White box testing

• uses an internal perspective of the system to design test cases based on internal structure. It requires programming skills to identify all paths through the software. The tester chooses test case inputs to exercise paths through the code and determines the appropriate outputs. In electrical hardware testing, every node in a circuit may be probed and measured; an example is in-circuit testing (ICT).

edit: just to clarify a bit more, I realize that both are important, but usually they are separate between dev and QA.

Is internal knowledge important for the tester/QA? I've heard arguments that testing with this knowledge in mind enables them to better test for problems, but I've also heard arguments that this knowledge can distract from functional needs and promote "testing to to the code" rather than to the intended solution.