INVEST Principles

<p>INVEST stands for Independent, Negotiable, Valuable, Scalable, and Testable.</p> <p>Whatever the negotiation process looks like, a story represents the melting point of an aspect of the system. Such an aspect ideally forms a thin functional slice through of the system. This makes the story self-contained. It provides full value for the end user as, once implemented, the described problem is solved and enfolds immediate value to the user.</p> <p>In addition, self-contained stories are better plannable as they are separated from other stories. Providing stories at this level let you decide on-the-go which story to implement next. This makes your planning quite flexible. It is not needed to follow (probably hidden) dependencies before reordering the stories.</p> <p>User stories should contain only the essence of all discussions and decisions to keep them short and clear. Details have to be avoided in the first place. It is recommended to start with a narrow scope and scale later when it becomes necessary. This helps to stay focused and avoid contradiction.</p> <p>To ensure a user story has been finished it should contain a list of acceptance criteria which the implementation could be (ideally) tested against. Testable criteria are very helpful when creating a solution for a problem. Each will support to understand the problem and could be used to validate an implementation against.</p> <p>In addition, there should also be an agreement on when implementing a story is actually done. The team normally agrees on a definition-of-done checklist which has to be worked through for each user story. In general, the definition-of-done includes an agreed set of tasks which have to be part of the result (e.g., unit-tests, documentation, ...).</p>