ranap
Joined: 28 Aug 2007
Posts: 13
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 Posted: Wed Aug 29, 2007 8:22 am Post subject: Black Box vs. White Box |
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The tendency is to relate equivalence partitioning to the so called black box testing which is strictly checking a software component at its interface, without consideration of internal structures of the software. But having a closer look on the subject there are cases where it applies to the white box testing as well. Imagine an interface to a component which has a valid range between 1 and 12 like in the example above. However internally the function may have a differentiation of values between 1 and 6 and the values between 7 and 12. Depending on the input value the software internally will run through different paths to perform slightly different actions. Regarding the input and output interfaces to the component this difference will not be noticed, however in your white-box testing you would like to make sure that both paths are examined. To achieve this it is necessary to introduce additional equivalence partitions which would not be needed for black-box testing. For this example this would be:
.... -2 -1 0 1 ..... 6 7 ..... 12 13 14 15 .....
--------------|---------|----------|---------------------
invalid partition 1 P1 P2 invalid partition 2
valid partitions
To check for the expected results you would need to evaluate some internal intermediate values rather than the output interface. |
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