Agile teams deliver software at the end of each sprint that is solid – very few defects, even if each sprint accommodates massive changes.
The only way to do this is through disciplined Agile Engineering practices – Test-Driven Development, Continuous Integration, etc. Teams write even the smallest unit of code in ways that catch defects early on, and in ways that easily and safely accommodate changes.
It is a point of pride of each of our teams to keep our codebase near-defect-free and deployable, not just at the end of each sprint, but at any given time. Our clients may or may not care about Agile, but they care about the results of the software they receive from us – solid software on which they can trust their business.