INVEST criteria
INVEST is a mnemonic for checking a user story, published by Bill Wake in 2003: Independent, Negotiable, Valuable, Estimable, Small and Testable. A story that meets all six can be ordered freely in the backlog, can still be discussed, delivers value, can be sized, fits inside a sprint and can be verified.
The longer version
Each letter is a question put to a draft story. Independent asks whether it can be scheduled without another story landing first. Negotiable asks whether the detail is still open to conversation. Valuable asks whether a user or customer would notice it. Estimable asks whether the team knows enough to size it. Small asks whether it fits inside a sprint, and Testable asks whether anyone could write a check that shows it done.
The letters pull against each other, so a story rarely scores perfectly on all six and the mnemonic works as a set of questions to argue over. Splitting a large story to make it Small can create stories that depend on one another, which costs Independence. A story that cannot be tested usually has vague criteria, and writing them fixes Testable and often Estimable in the same stroke.
The usual home for it is refinement, as a diagnostic. A story that fails Estimable generally needs a question answered. One that fails Small needs cutting into thinner slices of working behaviour. One that fails Valuable may be a task that belongs inside another story. Wake's article was titled 'INVEST in Good Stories, and SMART Tasks', and the second half of that title is the matching check for tasks.
Common questions
What does INVEST stand for in agile?
INVEST stands for Independent, Negotiable, Valuable, Estimable, Small and Testable. Each word is a quality a good user story has, and teams read the six as questions to put to a draft story during refinement.
Who created the INVEST criteria?
Bill Wake introduced the mnemonic in 2003, in an article called 'INVEST in Good Stories, and SMART Tasks'. The article gave agile teams a short list for judging whether a story was fit to be planned.
Does every story have to meet all six INVEST criteria?
Few stories meet all six cleanly, because the letters trade off against each other. Splitting a story to make it small can reduce its independence, so teams accept a weak letter when they know why.
What is the difference between INVEST and acceptance criteria?
INVEST judges the quality of the story itself, before the team takes it in. Acceptance criteria are the conditions attached to one story that say when it is done, and a story with checkable criteria already satisfies the Testable letter.
How do you make a story small enough for INVEST?
Narrow what the story covers while keeping something a user can try, for example one payment method first and the others in later stories. A cut that makes a story Small by leaving it with no value has traded Valuable for Small, which is the kind of trade-off the six letters exist to expose.
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