All-pairs testing

The term pairing method or English pairwise method is a method which is used in software testing to keep the number of tests of combinations of possible assignments of several input fields low. It is classified in the Black- box testing.

Definition

The basic idea of ​​the method is that it is often not necessary to test all possible combinations of inputs from multiple fields - it is often sufficient just to ensure that every field is tested in pairs with any other field in all combinations.

Is there, for example, an input form with three fields, which can take three different values ​​, so would have complete coverage of all possible combinations of 27 tests are performed:

With the pairwise method the number of tests can be reduced to nine:

Method

To go from a table with all possible combinations to a table by the pairwise method, one can use the following procedure:

Considering successively the row of the table from below to above. Are there any that occur in the observed line combinations of two values ​​again in one of the other lines, you can delete the considered row from the table. This one will continue until no more row can be deleted.

Comments

• With the pairwise method, under certain circumstances drastic reductions in the number of tests can be achieved. A table of 75 binary fields would result in a total of 275 (ie several trillion ) possible combinations - with the pairwise method ranging from 28 combinations.
• Errors that occur only with certain combinations of more than two fields ( so-called multi-mode faults ) are overlooked when using the pairwise method might!
• Creating the reduced tables can be very expensive - however, there are tools that remove this task the tester.

• Test (software)