Existing development standards and inspection checklists, for example, can provide a baseline for Cleanroom design and verification. Even code-based testing can coexist with Cleanroom as long as it is not substituted for usage testing. Implementation of the Cleanroom method can take place in a gradual manner. It will be too time consuming. Time spent in the design phase of a Cleanroom development is indeed likely to be greater than is traditionally devoted to design.
Time spent in test, however, is less than traditionally required.
One of Cleanroom's major objectives is to prevent errors from occurring. This is achieved by integrating formal methods for specification and design, and by using verification in place of unit testing prior to statistical testing. The purpose of Cleanroom testing is certification of reliability rather than removal of errors. Design and verification will require the greatest portion of the schedule. Testing may begin later and be allocated less time in the schedule than is ordinarily the case.