Without that, it will never really be known whether or how well the process is working, and whether it is worth the effort. This paper focuses on design and code reviews, although formal reviews can be applied to any stage of software development. While these rates are generally much better than that achieved by simply testing the end product, the kinds of errors found with each method are often quite different. In this sense, design and code reviews complement, rather than replace, testing as a tool for assuring quality software. A significant difference between inspections and testing, though, is that defects are identified and corrected in one step.
Testing simply identifies a defect-it reveals nothing about how to fix it.
Formal design and code inspections provide an effective means to catch defects early, where they are easiest and cheapest to fix. Reviews can actually take a number of forms, including management reviews, walkthroughs, code reading, and inspections. The first of these is usually a poor means of discovering problems, though it may serve other useful purposes. Design and code inspections, being the most formal kind of review, involve preparation by the participants, a meeting, and a formal inspection report. The Moderator handles the review logistics and ensures that the review materials and reviewers are prepared before allowing the inspection to proceed.