BlackBox Testing

Home | Dynamic Testing | Whitebox Testing | Unit Testing | Regression Testing

Blackbox testing takes an external perspective of the test object to derive test cases. The test designer selects valid and invalid input and determines the correct output.  This method of test design is applicable to all levels of software testing.This method of test design is applicable to all levels of software testing: unit, integration, functional testing, system and acceptance. The higher the level, and hence the bigger and more complex the box, the more one is forced to use black box testing to simplify. While this method can uncover unimplemented parts of the specification, one cannot be sure that all existent paths are tested.

Advantages of Black Box Testing

• more effective on larger units of code than glass box testing
• tester needs no knowledge of implementation, including specific programming languages
• tester and programmer are independent of each other
• tests are done from a user's point of view
• will help to expose any ambiguities or inconsistencies in the specifications
• test cases can be designed as soon as the specifications are complete

Disadvantages of Black Box Testing

• only a small number of possible inputs can actually be tested, to test every possible input stream would take nearly forever
• without clear and concise specifications, test cases are hard to design
• there may be unnecessary repetition of test inputs if the tester is not informed of test cases the programmer has already tried
• may leave many program paths untested
• cannot be directed toward specific segments of code which may be very complex (and therefore more error prone)
• most testing related research has been directed toward glass box testing