Techniques

The most common techniques are Black Box Testing, White Box Testing, and Error Guessing.

Testing techniques that examine the internal workings and details of a work product are said to use a white box approach. The technique which looks at how a Unit under test behaves by only examining its inputs and outputs is said to be a black box approach. The Error Guessing technique is where experience and intuition are applied to look for unexpected but prevalent errors.

Black Box Testing

In the Black Box approach, the testers have an “outside” view of the system. They are concerned with “what is done” NOT “how it is done”. Black Box testing is requirements and or specifications-oriented and is used at all test levels. The system or work product is defined and viewed functionally. To test the system, all possible input combinations are entered and the outputs are examined. Both valid and invalid inputs are used to test the system.

Examples of black box testing are:

enter an Automated Teller Machine withdrawal transaction and observe expected cash dispensed
exercising a programme function with external data and observing the results

White Box Testing

In the White Box approach, the testers have an inside view of the system, They are concerned with “how it is done” NOT “what is done”. White Box testing is logic oriented. The testers are concerned with the execution of all possible paths of control flow through the program. The “White Box” approach is essentially a Unit test method (which is sometimes used in the Integration test or in the Operability test) and is almost always performed by technical staff.

Examples of white box testing are:

testing of branches and decisions in code
tracking of a logic path in a programme

Error Guessing

Based on past experience, test data can be created to anticipate those errors that will most often occur. Using experience and knowledge of the application, invalid data representing common mistakes a user might he expected to make can be entered to verify that the system will handle these types of errors.

Examples of error guessing are:

hitting the ‘CTRL’ key instead of the ‘ENTER’ key for a PC application and verifying that the application responds properly