Agile Estimating and Planning (Robert C. Martin Series)

by Mike Cohn

Base estimates and plans on facts. Whenever possible, ground your estimates and plans in reality. Yes, there may be times in some organizations when it will be necessary to estimate things like velocity with very little basis in fact, and Chapter 16, “Estimating Velocity,” presented some valid techniques for doing so. However, whenever possible, estimates and plans should be based on real, observed values. This goes, too, for an estimate of how much of a feature is complete. It’s easy to tell when a feature is 0% done (we haven’t started it), and it’s relatively easy to tell when we’re 100% done (all tests pass for all of the product owner’s conditions of satisfaction). It’s hard to measure anywhere in between—is this task 50% done or 60% done? Because that question is so hard, stick with what you can know: 0% and 100%.