Non validating environment
A change of this scope is on the order of
A change of this scope is on the order of $1 (you do a little bit of retyping/remodeling).||
A change of this scope is on the order of $1 (you do a little bit of retyping/remodeling).
If you do not find it until the design stage, it is more expensive to fix.
With a TDD approach the feedback loop is effectively reduced to minutes - instead of the days, weeks, or even months which is typical in serial processes - and as a result there isn't on opportunity for the cost of change to get out of hand. Frankly all he's done IMHO is found a way to do what software engineering has recommended for a long time now, to test as early as possible - testing first is about as early are you're going to get. With XP you reduce the feedback loop through as well as by working closely with their customers (project stakeholders).(you do a little bit of retyping/remodeling).
This is due to the fact that as the system grows you simply have more to code, models, documents, and so on to work with, increasing that chance that your team will need to work with artifacts that they haven't touched for awhile.Or in the case of commercial software, or at least "customer facing" software that is used by the customers of your organization, the public humiliation of faulty software could be substantial (customers no longer trust you for example).Second, the cost to redeploy your system, as noted above, can be very large in some situations.If you do not find the problem until programming, you need to update your analysis, design, and potentially scrap portions of your code, all because of a missed or misunderstood user requirement.This error is on the order of 0, because of all the wasted development time based on the faulty requirement.