Pairwise testing, also known as all-pairs testing is the method of finding defects by using a combinational method of two test cases. It relies on the observation that most defects are caused by interaction of at most two factors. Hence a pair of two test parameters are chosen and all possible pairs of these two parameters are sent as input parameters for testing purpose.

Pairwise Testing leads to reduction in test cases and hence faster and easier testing capabilities. Higher order combinational testing has greater number of test cases, making the test more exhaustive but also more expensive as well as cumbersome. Moreover, most bugs are triggered by single input parameters or are caused by the interaction between two parameters. All these bugs can be taken care of by pairwise testing. Bugs caused by interaction between three or more parameters are usually very uncommon and provide very less justification for the greater investment in searching for them.