Should a pre and post test be the same?

Should a pre and post test be the same? Pre test and posttest should be same. You should not use a different topic. And its difficult to claim that the two different tests are of similar difficulty/discrimination level, because the evidences always differ.

Pre test and posttest should be same. You should not use a different topic. And its difficult to claim that the two different tests are of similar difficulty/discrimination level, because the evidences always differ.