What is Equivalence Partitioning?
Equivalence Partitioning (EP) is the process of methodically decreasing the huge set of possible test cases into a much smaller but still equally effective set. The goal of EP is to produce the set of possible test cases into a smaller, manageable set that still adequately tests the software. As we are choosing not to test everything, we are taking on risk. So we require being careful how to choose classes. Also note that EP is a set of test cases that test the similar thing or reveal the similar bug.