You may be aware of this, but this is as much a social/cultural discussion as it is a technical discussion.
Regarding requirements - they are always a live discussion, not just a list of things to do. Do not be surprised when they change, instead plan to manage how they change.
Regarding testing - think of testing as headlights on a car; they show potential problems ahead. Effectively all automated testing is regression testing. Unit tests are great for future developers working on that codebase, but no amount of unit tests will show that a SYSTEM works. You also need integration and exploratory testing. This isn't a matter of doing it right or wrong, it's a matter of team and technical maturity.
A bug is anything that is unexpected to a user. I'm sure this will be controversial, and I'm fine with that.
Regarding requirements - they are always a live discussion, not just a list of things to do. Do not be surprised when they change, instead plan to manage how they change.
Regarding testing - think of testing as headlights on a car; they show potential problems ahead. Effectively all automated testing is regression testing. Unit tests are great for future developers working on that codebase, but no amount of unit tests will show that a SYSTEM works. You also need integration and exploratory testing. This isn't a matter of doing it right or wrong, it's a matter of team and technical maturity.
A bug is anything that is unexpected to a user. I'm sure this will be controversial, and I'm fine with that.