Black Box Testing

Black box testing

Black box testing (sometimes called functional testing) is a software testing technique in which the tester has no knowledge of the internal workings of the software system or subsystem under test. The tester is aware only of the input data to be used, and what the expected outcomes should be. He or she never sees the programming code, and does not even need to understand how the program works in any detail.

This type of testing precludes the possibility of bias affecting the tester's evaluation of the software, since they are not involved in the software design process. It also means that testing is carried out very much from a user's perspective, and the tester is not required to be familiar with a particular programming language (or any program language at all, for that matter). On the down side, although test cases can be designed as soon as the software specification is complete, they can be difficult to design.

The time available for black box testing is usually limited, and it is not generally possible to test every possible path through the program. Black box testing can be applied to all levels of testing from unit testing right up to system testing. It is most frequently used for the higher levels of testing, however. As the size of the "box" becomes bigger, the complexity of the internal mechanisms increases rapidly, making black box testing the only practical option.