The acronym INVEST helps to remember a widely accepted set of criteria, or checklist, to assess the quality of a user story. If the story fails to meet one of these criteria, the team may want to reword it, or even consider a rewrite (which often translates into physically tearing up the old story card and writing a new one).
A good user story should be:
- "I" ndependent (of all others)
- "N" egotiable (not a specific contract for features)
- "V" aluable (or vertical)
- "E" stimable (to a good approximation)
- "S" mall (so as to fit within an iteration)
- "T" estable (in principle, even if there isn't a test for it yet)
- 2003: the INVEST checklist for quickly evaluating user stories originates in an article by Bill Wake, which also repurposed the acronym SMART (Specific, Measurable, Achievable, Relevant, Time-boxed) for tasks resulting from the technical decomposition of user stories.
- 2004: the INVEST acronym is among the techniques recommended in Mike Cohn's "User Stories applied", which discusses it at length in Chapter 2.