From The Mythical Man-Month by Fred Brooks: """ No parts of the schedule are so thoroughly affected by sequential constraints as component debugging and sys

From The Mythical Man-Month by Fred Brooks: """ No parts of the schedule are so thoroughly affected by sequential constraints as component debugging and system test. Furthermore, the time required depends on the number and subtlety of the errors encountered. Theoretically this number should be zero. Because of optimism, we usually expect the number of bugs to be smaller than it turns out to be. Therefore testing is usually the most mis-scheduled part of programming. For some years I have been successfully using the following rule of thumb for scheduling a software task: 1/3 planning 1/6 coding 1/4 component test and early system test 1/4 system test, all components in hand. This differs from conventional scheduling in several important ways: 1. The fraction devoted to planning is larger than normal. Even so, it is barely enough to produce a detailed and solid specification, and not enough to include research or exploration of totally new techniques. 2. The half of the schedule devoted to debugging of completed code is much larger than normal. 3. The part that is easy to estimate, i.e., coding, is given only one-sixth of the schedule. """