Explain the mechanism of pairwise testing and its main principles.

Pairwise testing is a test design technique aimed at reducing the number of test cases when checking parameter interactions. The main idea is that most errors occur due to interactions of no more than two parameters, so it is sufficient to test all possible pairs of parameter values.

Working principles:

• Parameters and their possible values are defined.
• A set of tests is formed that covers all possible pairs of parameter values at least once.
• This significantly reduces the number of tests compared to a full enumeration of all combinations.

For example, if there are 3 parameters with 3 values each, a full enumeration would require 27 tests, while pairwise testing can reduce this to 9-10, while still covering all pairs.

This approach is effective for systems with a large number of parameters, where full enumeration is impossible due to exponential growth in the number of tests.