It depends what do you expect from tester and what kind of tasks. You should understand that test engineer which care about users and understand code, could find narrow costs much more :) I believe it's desirable that manual test engineer can read code but not necessary. But if you mean automation test engineer or common QA engineer (manual and sometimes automation) it's necessary though to understand project archicture and read the code.

It depends what do you expect from tester and what kind of tasks. You should understand that test engineer which care about users and understand code, could find narrow places in code costs much more :) I believe it's desirable that manual test engineer can read code but not necessary. But if you mean automation test engineer or common QA engineer (manual and sometimes automation) it's necessary though to understand project archicture and read the code.