INVEST story principles

Good user stories follow Bill Wake’s INVEST model. They are Independent, Negotiable, Valuable, Estimable, Small, and Testable.

  • I - Independent
  • N - Negotiable
  • V - Valuable
  • E - Estimable
  • S - Small
  • T - Testable


Stories should be independent, would be good if they are not overlapping.


A good story captures the essence, not the details.


A story should be valuable to the customer, not for anybody. If think of a product like a cake, we want to give the customer the essence of the whole cake, and the best way is to slice vertically through the layers.


A good story can be estimated. We don’t need an exact estimate, but just enough to help the customer rank and schedule the story’s implementation.


Smaller stories tend to get more accurate estimates.


“Testability” has always been a characteristic of good requirements. Actually writing the tests early helps us know whether this goal is met.

How to split