... Finally, we fix a defect by exposingan API in b o th classes, and then we refactor the APIs into a single API in the base class.12.1 RefactoringThe first step in continous design is to b e sure ... happens,and it involves two activities: changing what the code does and improvingits internal structure. In XP, these two activities have names: implementing stories and refac-toring. Refactoring is ... operate, even after years of planning.2Somepeople call this maintenance programming, implementing change requests,or, simply, firefighting. In XP, it’s called continuous design, and it’s the onlyway...