Should black box or white box testing be the emphasis for testers?

Question

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

Answer 1

Simple...Blackbox testing is otherwise known as Integration testing or smoke-screen testing . This is mostly applied in a distributed environment which rely on event-driven architecture. You test a service based on another service to see all possible scenarios. Here you cannot completely forecast all possible output because each component of the SOA/Enterprise app are meant to function autonomously. This can be referred to as High-Level testing

while

White box testing refers to unit-testing. where all expected scenarios and output can be effectively forecasted. i.e Input and expected output.This can be referred to as Low-level testing

Answer 2

Here is my 5 cents:

As a developer, I mostly write tests for methods (in a class) as white box tests, simple because I do not want my test to break just because I change the inner works of my code.

I only want to my tests to break if my method behavior changes (e.g. returns a different result than before).

Over the last 20 years of development, I simple got tired of doing up-to double work just because my unit tests was strongly tied to the code and I need to maintain both application code and test code.

I think making decoupling code (also when you code tests) is a very good practice.

Another 5 cents: I hardly never use mocking frameworks, because when I find it necessarily to mock something I prefer to decouple my code instead - and yes in many cases that is very possible (especially if you are not working in legacy code) :-)

Answer 3

• *Black box testing: Is the test at system level to check the functionality of the system, to ensure that the system performs all the functions that it was designed for, Its mainly to uncover defects found at the user point. Its better to hire a professional tester to black box your system, 'coz the developer usually tests with a perspective that the codes he had written is good and meets the functional requirements of the clients so he could miss out a lot of things (I don't mean to offend anybody)
• Whitebox is the first test that is done in the SDLC.This is to uncover bugs like runtime errors and compilation errrors It can be done either by testers or by Developer himself, But I think its always better that the person who wrote the code tests it.He understands them more than another person.*

Answer 4

"Both" has been stated above, and is the obvious answer...but IMO, white box testing goes far beyond developer unit testing (althoughI suppose it could depend on where you draw the line between white and black). For example, code coverage analysis is a common white box approach - i.e. run some scenarios or tests, and examine the results looking for holes in testing. Even if unit tests have 100% cc, measuring cc on common user scenarios can reveal code that may potentially need even more testing.

Another place where white box testing helps is examining data types, constants and other information to look for boundaries, special values, etc. For example, if an application has an input that takes a numeric input, a bb only approach could require the tester to "guess" at what values would be good for testing, whereas a wb approach may reveal that all values between 1-256 are treated one way, while larger values are treated another way...and perhaps the number 42 has yet another code path.

So, to answer the original question - both bb and wb are essential for good testing.

Answer 5

Black Box Testing: Black Box testing is just observation no need Internal Knowledge or structure of software product. just putting valid and Invalid data input and expecting the correct result. here tester find the defect but unable to Find the Location of defect.black box testing done in all testing level.

Black box testing tecniques are: 1. Equivalance partition 2. Boundary Value Analysis 3. Decision table 4. State Transition Diagram 4. Use case diagram

White Box Testing: White box is testing it requires the knowledge of internal logic and structure of software product. here we will check the loop, condition and branch. here we find not only the defect but also and location of defect.

White box Testing Techniques: 1. Statement Coverage 2. Decision Coverage 3. Branch Coverage 4. Path Coverage.

Answer 6

It's a bit of an open door, but in the end both are about equally important.

What's worse?

1. software that does what it needs to do, but internally has problems?

2. software that is supposed to work if you look at the sources, but doesn't?

My answer: Neither is totally acceptable, but software cannot be proven to be 100% bugfree. So you're going to have to make some trade-offs. Option two is more directly noticable to clients, so you're going to get problems with that sooner. On the long run, option one is going to be problematic.