A product can be of low quality for several reasons, such as it was shoddily manufactured, its components were improperly designed, its architecture was poorly conceived, and the product's requirements were poorly understood.
Quality must be designed in. You can't test out enough bugs to deliver a high-quality product. The quality assurance (QA) process is vital for the delivery of a satisfactory system. In this last part in this series, we will concentrate on portions of the methodology particularly aimed at improving the quality of the resulting system.
The software testing techniques described earlier in this series constitute one component of quality assurance, but the pursuit of quality extends throughout the design flow. For example, settling on the proper requirements and specification cannot be overlooked as an important determinant of quality. If the system is too difficult to design, it will probably be difficult to keep it working properly.