The last method is referred to in our shop as the A0 method. We have selected the first option. We believe it is the easiest to implement and provides the best long-term value for the effort we will expend. If we are going to change the system, we may as well change it to what it would be if we were designing it today. In our opinion, the other two processes are temporary measures.
New software operates correctly where the turn of the century is involved.
This is of major importance to us because of the way days are calculated. We will be concentrating most of our time on constructing tests involving this scenario. The users are the people responsible for moving product out the door. Thus, they are the ones in the frontline trenches and will be most affected if problems arise. It is in their best interest to design and implement system tests to ensure that the upgrade is successful.