Evaluation of Black-Box Testing

Faulty specifications or requirements are not revealed

All black-box testing techniques are based on the requirements and/or specifications of a system or its components and their interactions. If the requirements include erroneous definitions or an erroneous specification was used as the basis for an implementation, black-box testing will not reveal these defects. This is because there will be no deviation between the erroneous requirement and the system’s actual behavior—i.e., the test object behaves as specified, even if the specification is erroneous. If a tester uses common sense and views requirements critically, erroneous requirements can be identified when designing test cases. Otherwise, you will need to schedule reviews to identify inconsistencies and defects in the specifications.

Non-required functionality is not recognized

Black-box techniques are also not able to check whether the test object has other functionality that goes beyond the actual specifications (often a reason for security issues). These additional functions are neither specified nor are they part of the customer’s requirements, and test cases that cause them to be executed are only performed coincidentally, if at all. The coverage criteria that determine when testing is complete are based entirely on the requirements/specifications, not on functions that haven’t been described and whose existence is only surmised.

Checking basic functionality

The focus of all black-box testing techniques is the functionality of the test object. It is certainly undisputed that the correct functioning of a software system has the highest priority and thus black box test procedures must always be used.