We have got an old system "Qwerty1" - that makes a lots of things,
then we also have got another system "Querty2" it's actually a remake of Qwerty1
(for several reasons) Notice we still are live with "Qwerty1".
now we want to to be sure for all tested indata in Qwerty2 we get the same outputdata in the both systems.
What is this methodology called?
Thank you in advance