Its far better to tell, yes i did test with this scenario, but now am not accurate with it rather than, I did test this scenario before and it was working fine.
All because, Anything may happen to the software at any time. You see, we cant able to be sure whether we have the same tested code moved to live all times., You don know, you cant able to control the things happened in software beyond your hands.
One software tested by the tester and got approved by him after the 10+ number of iterations. Finally code get moved to live server, One particular scenario not work properly in live server, client experience the same issues and shoot out to tester. Tester got amazed, because that particular case already raised as bug by him and get closed in one of the iteration, but now the issue exists in live server.,
There may be number of reasons behind the scene.
Tester raised N number of bugs in first iteration send the report to development team. Development team fixed the bugs and sent updated code to tester. Again tester tested the application, cross verify the N number of bugs get resolved or not, if the bugs resolved means change the status of the bug, if not means reopen it and sent report to development team, same time this iteration test again found N+ bugs. In third iteration, tester test with the reopen bugs and the new one raised in iteration 2. So then what will happen to the bugs closed state in Iteration 2 ?
Normally the testing time gradually decreases in every additional iterations. so is in it possible to to test all the test cases in every iteration? It is a challenging thing to deal with, :(