Commonality and Variances Testing
A technique to develop test cases based on similarities and differences.
Group together test situations, based on what they have in common. Two or more situations are equivalent if the successful test result from one situation means that the others would also work successfully and thus do not need to be separately tested. For tests that are equivalent, execute only (a) a representative or random example of all the possible tests, or (b) the worst-case test. Identify the variances that are not covered by these common tests, and ensure these variances are covered in testing also.