After several iterations of testing and fixing periods, we should have got to a stage where all valid outstanding issues have been converted into a full scale change request because they are a scope change, closed down, fixed or are of such a low priority that we can proceed without a fix. We should make sure the change requests are properly documented, prioritized, and the work needed for the change is estimated.
Stepping back from the issues, is the original concept proved? Do our stakeholders buy into the system we've built? Is our sponsor on board and happy that this phase is complete? If the answer to these questions is yes, then we have achieved everything we wanted to from our proof of concept. Our system is fit for purpose and adequately supports the business process. We are now ready for full-scale UAT followed by go-live.