Which of the following describes equivalence partitioning?

Equivalence partitioning is a test design technique that involves dividing input data into distinct categories or "partitions" that are expected to exhibit similar behavior. The core idea is that if a particular input from one partition works as expected, all other inputs in that same partition will behave similarly and should also be processed correctly by the system. By identifying these partitions, testers can create representative test cases that reduce the total number of test cases needed while still covering a wide range of scenarios.

This technique is particularly useful because it allows testers to focus on meaningful data rather than testing every single possible input. By ensuring that each partition is adequately tested with just one representative value, the effectiveness and efficiency of the testing process are significantly improved.

The other options refer to different concepts that do not align with the principles of equivalence partitioning. For instance, testing all possible input values would lead to excessive test cases, making it impractical; stress testing focuses on determining the system's robustness under extreme conditions, which does not correspond to assessing equivalence classes; and ensuring uniqueness of test cases is a separate concern that does not explore the concept of partitions and their equivalence.