Code Complete, 2nd Edition

When to Do Quality Assurance

As Chapter 3 noted, the earlier an error is inserted into software, the more entangled it becomes in other parts of the software and the more expensive it becomes to remove. A fault in requirements can produce one or more corresponding faults in design, which can produce many corresponding faults in code. A requirements error can result in extra architecture or in bad architectural decisions. The extra architecture results in extra code, test cases, and documentation. Or a requirements error can result in architecture, code, and test cases that are thrown away. Just as it's a good idea to work out the defects in the blue-prints for a house before pouring the foundation in concrete, it's a good idea to catch requirements ...