Project teams generally use three types of quality management activities:
- Quality planning
- Quality control
- Quality assurance
The purpose of quality assurance is to prevent as many errors as possible by having sound processes in place to begin with. The purpose of quality control is to inspect or test the deliverables to find as many remaining errors as possible.
One important aspect of quality control is to find errors and defects as early in the project as possible. Therefore, a good quality control process will end up taking more effort hours and cost upfront. However, there will be a large payback as the project progresses.
For instance, it's much better to spot problems with business requirements during the analysis phase of the project rather during the testing process. If you see the problem during the requirements gathering process it might just take a call to your client and the quick update of a Word document to fix it. On the other hand, if you discover this problem in the testing phase, it could impact the business requirements, the solution design, and some of the construct work. It will also require you to re-test the solution again. As you can see, this is a potentially huge impact to your project.
Likewise, if you were manufacturing a computer chip, it would be much cheaper to find a problem with a computer chip when the chip is manufactured, rather than have to replace it when a customer brings the computer in for service after a purchase. In fact, if the error isn't caught until after the chip is sold to the customer, the cost to make the repair might cost more that the entire cost to manufacture the product to begin with.
There was a project early in my career that applied poor shortcuts to the development process. Since the programmers were under time pressure to complete their modules, they figured they would write the code and make sure it compiled cleanly. Then they would then call the module complete, with the attitude that they could "fix it in the testing phase." They thought that they were just deferring their unit test time until later in the project. But by pushing these errors further downstream, it actually took much longer to fix the problems later - to the detriment to the overall project.
On many projects the team plans to find as many errors as possible during the testing process, with some errors not caught until support/maintenance.In Figure B we see the better approach. It is much better to catch any errors that are introduced as quickly as possible. In other words, errors in the deliverable created in the Analysis Phase should be caught in the Analysis Phase; errors introduced in the Design Phase should be caught during the Design Phase, etc. This greatly minimizes the impact of correcting the errors.
The bottom line is that the project team should try to maintain high quality and low defects during the deliverable creation processes, rather than hope to catch and fix problems during the testing phase at the end of the project (or worse, have the client find the problem after the project has been completed).