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nazeer

nazeer (Querist)
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09 June 2012 what is meant by block box approach and white box approach

CA Ghanshyam Joshi

CA Ghanshyam Joshi (Expert)
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11 June 2012 (II) Dynamic Analysis Testing
• Black Box Testing : 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 inputs and determines the correct output. There is no knowledge of the test object's internal structure.
This method of test design is applicable to all levels of software testing : unit, integration, functional testing, system and acceptance. The higher the level, 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. If a module performs a function which is not supposed to, the black box test does not identify it.
• White Box Testing : 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. Since the tests are based on the actual implementation, if the implementation changes, the tests probably will need to change, too. It is applicable at the unit, integration and system levels of the testing process, it is typically applied to the unit. While it normally tests paths within a unit, it can also test paths between units during integration, and between subsystems during a system level test. After obtaining a clear picture of the internal workings of a product, tests can be conducted to ensure that the internal operation of the product conforms to specifications and all the internal components are adequately exercised.
• Gray Box Testing : Gray box testing is a software testing technique that uses a
combination of black box testing and white box testing. In gray box testing, the tester applies a limited number of test cases to the internal workings of the software under test. In the remaining part of the gray box testing, one takes a black box approach in applying inputs to the software under test and observing the outputs.