If Developers Nail Estimates, They Are Lying To You
Often is seen as maturity and sign of expertise, the fact of being able to give specific and reliable estimates. But that goes against the nature of software development itself.
How reliable are estimates?
The most difficult work in the software development is grasping the exact requirements. I often say that once we know exactly what we have to do, the job is done. That is because the job of the developer is translating the customer needs into computer code, but the effort is not in the translation itself, but in the definition of all possible scenarios. The computer does not tolerate ambiguity, so the developer has to spend a most of the effort thinking and solving all missing requirements.
And that is the first factor that affects the reliability of estimates. The finest is the detail in the requirements, the more reliable are the estimates. Any uncovered detail may explode in new consequences that may affect other requirements, and affect the total final required time. That is why, often, developers decompose stories in smaller tasks to get better estimates. But the effort may not be worth it.
