INVEST: It’s Not What You Think

Many Agile people use the INVEST criteria. Giles, the Agile coach we had on our team, made INVEST part of our definition of ready. But INVEST is more radical than he realised.

INVEST says that user stories should be Independent, Negotiable, Valuable, Estimable, Small and Testable.

INVEST was proposed by Bill Wakes in 2003. His original article is here. His thoughts on “Estimable” and “Negotiable” might surprise you…


For may teams, estimating stories is a big part of their process – it can take up several hours a week and be the focus of much of the team’s conversations (refinement, retrospectives, etc).

Bill Wakes’ original article says estimation should be “just enough to help the customer rank and schedule the story” but in a 2015 update he says that if could re-invent INVEST then estimation would NOT be a part of it.

Estimability is the most-abused aspect of INVEST (that is, the most energy spent for the least value). If I could re-pick, we’d have “E = External [Impact]”

Bill Wakes, 2015

I’ll come back to External Impact in a minute but first, what do we do if estimable isn’t a key criteria for stories? Bill gives three alternatives: (1) Order Of Magnitude, (2) Historical Estimates, and (3) Count the Stories. Detail in his article.

External Impact

Bill Wakes talks more about External Impact in this article

“real” stories: they start from outside the system and go in

In other words: be user-centric.

Being user-centric means focusing on the things that really make a difference to users. It means focusing not on outputs, or even outcomes, but IMPACT.

To focus on impact you need to see the big picture. This is harder than it sounds. The best way to get a perspective is to be smart about data. I highly recommend the book “The Data Detective“.


For many teams, having detailed requirements is necessary before a story can be scheduled, but INVEST tells us something different…

[A story] is not an explicit contract for features; rather, details will be co-created by the customer and programmer during development. A good story captures the essence, not the details. Over time, the card may acquire notes, test ideas, and so on, but we don’t need these to prioritize or schedule stories.

Bill Wakes, 2003


INVEST is a really helpful guide to working effectively. It’s more radical than it seems!

What do you think? Leave a comment below.

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