A former client asked:

“What does Scrum say about User Acceptance Testing? I am wondering if it should best be done within 24 hours of delivery, or at the end of a sprint…“

I’ll dodge scrum, but answer how we do it here by framing this in terms of risk and velocity:

We prefer to get acceptance as soon as a story can be delivered to the acceptance/demo server. Intra-day is the best, but certainly within the same sprint when the work is done so as not to muddy velocity measures (a story isn’t done until it is accepted, so there’s incentive on all sides).

The longer a story sits out there (waiting to be accepted), the bigger the risk that it is “wrong” and needs re-work. Since the code base continues to evolve, fixes are harder the further they are away (in terms of commits) from the original change-set. This can slow down velocity. We want to reduce risk and maintain a steady velocity. Thus, the sooner a story is accepted by the stake holder, the better.