What is a user story?

Definition: A listing of acceptance criteria needed to deliver a new feature or piece of work. Generally written from the perspective of a user of the system. A commonly used format is: As a X, I want to Y, so that Z

Kent Beck first introduced the term as part of Extreme Programming to encourage a more informal and conversational style of requirements elicitation than long written specifications. The essence of a story can be written on a single note card.

A user story is a statement of user functionality formulated as a few sentences in the everyday language of the user. The user story represents a placeholder for a later conversation regarding details and acceptance criteria.

A user story represents a small piece of business value that a team can deliver in an iteration. Stories are deliberately not fleshed out in detail until they are ready to be developed, you only need enough understanding to allow prioritization with other stories. While traditional requirements (like use cases) try to be as detailed as possible, a user story is defined incrementally, in three stages:

  • The brief description of the need
  • The conversations that happen during backlog grooming and iteration planning to nail down the details
  • The tests that confirm the story’s satisfactory completion

Well-formed stories will have the below characteristics as defined by Bill Wake with INVEST mnemonic:

Why use user stories?

  • Keep yourself expressing business value
  • Avoid introducing detail too early that would prevent design options and inappropriately lock developers into one solution
  • Avoid the appearance of false completeness and clarity
  • Get to small enough chunks that invite negotiation and movement in the backlog
  • Leave the technical functions to the architect, developers, testers, etc.

How do I write user stories?

When you’re getting started with stories, a template can help ensure that you don’t inadvertently start writing technical tasks:

As a , I want to so that .

  • As a delivery team member, I want to know which tasks I own so that I can decide what to work on now.
  • As a developer, I want to know which of my stories have failing test cases so that I can fix the code.
  • As a product owner, I want to be able to drag-and-drop prioritize all the product backlog items, so that I can easily adjust priorities based on changing needs.

Try to avoid the generic role “User” when writing user stories. User stories are about all of the “actors” who interact with the system or who realize some value or benefit from the system. Not all actors are end users. For example, an actor could be another system or someone who wants certain functionality in order to buy your product but will never actually use the product. It may be useful to create aggregate actors (e.g. “consumer”) and specialized actors (e.g. “browser” or “frequent shopper”).

What size should a user story be?

A story should be small enough to be coded and tested within an iteration- ideally just a few days. When a story is too large, it is called an “epic”. Backlog items tend to start as epics, when they are lower priority. For release planning, epics should be broken down into smaller chunks, but not so small that you’ve moved into detailed design.

How detailed should a user story be?

Too broad

  • “A team member can view iteration status.”

Too detailed

  • “A team member can view a table of stories with rank, name, size, package, owner, and status.”
  • “A team member can click a red button to expand the table to include detail, which lists all the tasks, with rank, name, estimate, owner, status.”

Just right

  • “A team member can view the iteration’s stories and their status, with main fields.”
  • “A team member can view the current burndown chart on the status page, and can click it for a larger view.”
  • “A team member can view or hide the tasks under the stories.”
  • “A team member can edit a task from the iteration status page.”

Who uses user stories?

Creation — The customer, customer proxy, product owner and anyone else who identifies a need for the product can contribute user stories.
Ownership & Maintenance — The product owner owns the user stories and is responsible for writing, gathering, maintaining, and prioritizing.
Usage — Developers, testers, technical writers use user stories to be able to know what to implement and when they’re done. Product owners track overall progress based on the status of the user stories. Management tends to track user stories rolled up to epics or features.

What are the top 3 mistakes that people make?

  1. Too formal / too much detail. Product owners with good intentions often try to write extremely detailed user stories. If a team sees a story at iteration planning that looks like an IEEE requirements document, they’ll often assume that all the details are there and they’ll skip the detailed conversation.
  2. Technical tasks masquerading as stories. A lot of the power of Agile comes from having a working increment of software at the end of each iteration. If your stories are really just technical tasks, you often don’t end up with working software at the end of each iteration, and you lose flexibility in prioritization.
  3. Skipping the conversation. Stories are intentionally vague before iteration planning. If you skip the acceptance criteria conversation, you’ll risk moving in the wrong direction, missing edge cases or overlooking customer needs.