Tag Archive for: agile

Story Points

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Don’t use hours to estimate a requirement or feature.  Your estimate will be wrong, but you’ll be held to it.  Instead let’s use story points.  Story points are values that only have meaning within a given team.  That meaning is developed, learned, and refined over time.

 To understand story points, let’s look at something similar that we all understand.

Restaurants are rated on a scale of 1 to 5.  That star rating conveys a lot of information.  With that star rating you know the following:

  • Quality of food
  • Attire
  • Price
  • Wait time for food
  • Will there be valet parking?
  • Will there be a waiter or do I order at the counter?
  • How customizable will the meal be?
  • How knowledgeable will the staff be?

If I tell you we are going to a 5 star restaurant, I bet you could answer all of those questions with a high degree of confidence.  You would not know precisely how much it will cost, but you’ll have a ballpark feel for it.  If tell you we are going to a 2 star restaurant, again, I bet you have a pretty clear expectation.

If instead of the star rating, I just told you that the food was really good, would you know how to dress?  If I just told you that it was very reasonably priced, would know if you were ordering at the counter or talking to a waiter.  If told you that meals were $50 a plate, you might guess that it was a 4 or 5 star restaurant.  But in reality it could be a 3 star tourist trap on an island that has only 1 restaurant and has to fly all of their food in from the mainland.  The point being is that knowing only one dimension can sometimes you get close to the right answer, but can also be quite misleading and dangerous.

Story points allow you to embed information from lots of dimensions into the numeric value.  We might embed the following dimensions into our story points:

  • Coding effort
  • Complexity
  • Risk
  • Knowledge of technology
  • Quality of the domain expert
  • Platform
  • Usability requirements

So maybe we can setup story points like the following:

Example:

  • 1 point = easy, straightforward feature
  • 2 points
  • 3 points = moderate, somewhat complex feature or contains some moderate risk
  • 4 points
  • 5 points = hard, complex feature, that may contain high risk

These are just guidelines to get started.  Story points develop meaning over time.  Just as with restaurants, it took experience with restaurants before you understood the rating system.

In that one number you can embed any additional information or padding that you may need.  If you estimate everything in hours you will be challenged by people who don’t know better.  If you assign story points to things, you can use your intuition or any other knowledge to pad your estimate without getting into a debate with those who don’t understand.

Each developer will bring a different intuition to assign story points.  Some will be junior developers who spend most of their time focused on technology challenges.  Others will be senior architects who are assessing risks and future complexities far outside the experience of the junior developer.  Story points serve to normalize those large differences in experience and perspectives across the team.

Story points are a tool.  When used incorrectly you will get bad results.  Story points only work when the project is being managed in the Scrum (or similar) methodology. They work with time boxed sprints and user stories.  If you are doing time boxed sprints and user stories, then you may not get the desired results.

User Stories

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What is a user story?

A user story is one or more sentences describing what a end user needs.  It is expressed in everyday language or the business language of the user.  A user story is NOT intended to capture ALL knowledge required to implement a given feature.  User stories facilitate conversations between customer and developer.  The details required to implement the story are acquired overtime via these conversations.  

Why user stories?

  • Verbal communication – yields greater knowledge and understanding
  • Comprehensible (non technical)
  • Right size for planning
  • Work well with iterative development
  • Encourage deferring detail
  • Opportunistic development
  • Participatory design (between developers and customer)
  • Build up tacit knowledge

Structure of a User Story

As a {user role} I want to {do something} so that {reason} 

  • User Role = Who
  • Do Something = What
  • Reason = Why

 NOTE: we are not talking about HOW to implement it.

The structure of the sentence forces us to talk about requirements and NOT design.  This prevents us from short-circuiting the analysis and design phases.

Attributes of a good user story

Very good blog explaining the important attributes of a user story

http://agilesoftwaredevelopment.com/blog/vaibhav/good-user-story-invest

Just think of INVEST to remind you of the attributes of good user story.

  • Independent – loose coupling between user stories.  Makes planning much easier.
  • Negotiable – don’t design a solution or specify so many details that you paint yourself into a corner.  We should always be free to change our mind on HOW to implement the given requirement at a later time.
  • Valuable – must be a value to the end user
  • Estimable – must be able to put an estimated number of hours or days
  • Small – less than a week
  • Testable – so we know when we are done.

A useful tool for ensuring that user stories adhere to INVEST is to either break a user story apart into smaller user stories.  Occasionally, the opposite might be true (combine many smaller use stories), especially in support of Independent.

Drawbacks to User Stories

  • Difficult to understand relationship between stories
  • May require augmenting them with additional documentation if traceability is a mandate
  • May not scale well to large teams (too much conversation and too many pathways)

Guidelines for Good Stories

  • Start with Goal Stories – why is user using the system?
  • Slice the Cake – slice up large stories in way that the user can actually accomplish something (not part of something).  e.g. 1) collect data 2) write to database.  That is bad.  Good would be to 1) collect basic information, 2) collect detailed information
  • Write closed stories – don’t write a story that will never complete.  e.g. A user can manage his projects.  instead, breakup into smaller chunks that can be completed.  e.g. A user can add and remove team members from a project.
  • Put constraints on cards
  • Size the story to the horizon – stories you are going to tackle sooner need more precision.  Stories far in the future don’t need same level of precision.
  • Keep the UI out as long as possible – that’s a design task, not a requirements task
  • Some things aren’t stories – if it does not fit in a user story, use a different method.  Use this is a last resort, not as a cop out to learning how to write good user stories.
  • Include user roles in stories
  • Write for one user
  • Write in active voice
  • Customer writes – ideally, but requires training and discipline on the part of the customer
  • Don’t number story cards – tempting, but pointless overhead.  Short title is better.
  • Don’t forget the purpose – to remind you to discuss the feature

Final Thoughts

User stories are a TOOL.  They are a great tool that every software developer should master.  But like any tool, it can be misused and thus not yield the desired results.  Also, like any tool, it is not appropriate for every job.  Before you try to use this tool, I highly recommend reading some books, reading blogs of those who have had success, and start small.

Books