With all these scenarios I came to realize the following: The beauty of SCRUM is, everything is an estimation. The not so beautiful part of SCRUM is… that everything is an estimation and not everyone understands that. So here are some things my team and I applied in past and current projects:
Last thing, remember we all are a team, Devs, QA, design, DBA, etc. Throw away that old (and dumb) idea of us versus them or Dev vs QA, because that’s not how this works. We are all in the same boat, and we share the same goal, which is to deliver a high-quality product.
I hope my experience helps your transition to SCRUM to be a bit easier, and helps you understand what can be done and accomplished. SCRUM is here to stay. Happy stand-ups!