User stories and Use cases are both used to document the requirements. They both capture features of the system. They’re both used by the development team to construct the best solution. They can be used to organize and categorize requirements. And they can be used as references during testing to ensure that the requirements have been met. While user stories and use cases are similar, they also differ in substantial ways. The difference can be challenging to understand and explain, especially if your team is making a transition from a Waterfall software development environment to Agile and Scrum. Each serves a distinct purpose, and they both have their place on a well-run software project. We will try and cover User story vs Use case in this article…
What is a User story
As the name suggests – it’s a story from users’ perspective. What story? Obviously the description of a required software feature. What’s different? The perspective! The User story focus on who the feature is for, what they want to accomplish, and why rather than what system can do.
- As a <user type>, I want to <function> so that <benefit>
- As a <type of user>, I want <some goal> so that <some reason>
- As a <role>, I want <goal/desire> so that <benefit>
- As <who> <when> <where>, I <what> because <why>
- As a <type of user> I want <to perform some task> so that I can <achieve some goal/benefit/value>
What is a Use Case
Use Case is a set of interactions between a system and one or more actors, with actors being people, other systems, or both. It’s a complete specification of all possible scenarios. They are usually created as documents, and generally include this kind of information:
- Use case title & description
- Standard path or main success scenario
- Alternate paths or extensions
- Post conditions
Use cases focus on how your system interacts with other systems and actors and are typically extremely detailed. Traditionally, these are written by a single person or a small group of people and require someone else to sign off on them.
User story vs Use case
Documentation vs. Conversations
User Stories deliberately leave out a lot of important details. User Stories are meant to elicit conversations by asking questions during review. As the product owner presents the stories, the team will ask questions to further clarify the user story and the acceptance criteria. They rely on this collaboration. User story vs Use case: Developing small increments, getting feedback and iterating, rather than having more detailed documentation up-front as in Use cases.
Rigid vs. Agile
User Stories are deliberately abstract early on in a project and will evolve over time on a just-in-time and just-enough basis. This is because agile projects expect and anticipate change and respond to this change by adapting the product to the evolving needs. This is in stark contrast to Use Case thinking where the goal is to define various flows of the use case and all the details of the requirements up front. Use Cases are meant to provide such a formalized blueprint of the project that they often leave little room for negotiation or project additions. In agile we want to evolve the solution iteratively and incrementally as we learn based on feedback from real customers/users, not rework the documentation and requirements. The product owner can refine the original acceptance criteria in response to new information throughout a user story’s progress.
System behavior vs. User needs
Traditional requirements are usually thought of as capabilities and constraints of the system; the key term being system. All good requirements describe what the system can do or shouldn’t do, but those requirements that focus intensely on the system tend to de-emphasize user interaction or business context related to the user or business. To be fair, many traditional requirements do provide context for business and users, but that is usually not the main focus of the requirement, rather it’s the system that is the focus. The difficulty with having the system be the focus is that it’s easy to make assumptions about what the user wants. This is what really makes traditional requirements tough: They’re written from the system perspective.
When you write a user story, what you’re describing is a “raw” user need. User stories focus on customer value with a built-in imprecision meant to encourage communication. Use case typically has a lot of detail, and describes everything that the developer needs to build in order to meet the user’s need. That’s why it needs to have a lot more detail, and be clear and unambiguous.
System vs. Business language
Use Case can get a bit complicated and isn’t a format that is generally palatable for end users or business people. It is more complex and attempts to be complete, accurate, and handle all possible cases. A lot of effort it expended to make sure it’s correct. During development, it’s intended to be able to answer any questions about customer requirements so that team may proceed without having to track down the customer.
User Stories on the other hand are very simple and easy to understand. When you write a user story, what you’re concentrating on is writing something that anyone can understand. They are written from the point of view of a person using your application, and written in the language that your customers would use. It’s incomplete, possibly inaccurate, and doesn’t handle exceptional cases because not a lot of effort is expended making sure it’s correct. During development, it serves as a reminder and a starting point for additional discussions with the customer about the full extent of his needs.
Detailed vs. Precise
A use case goes into significantly greater detail than a user story. Use case documents (also called “use case specifications”) can be many pages long. Use cases capture the details of an interaction between the user and the system, and good use case specifications leave no stone un-turned. A user story is a shorter, more precise statement about what user X wants from system Y, and includes the business value Z associated with the interaction. They do not include detailed business rules, data specifications, usability standards, or any other detailed requirements beyond a simple description of the feature itself.
User stories are written in native language and often follow the structure: As a [user role], I want to [goal], so I can [reason]. Use cases capture a lot more information for example: Pre-condition, Post-condition, Trigger, Actors involved, Verbal description, sequence of actions etc.
Execution vs. Planning
Priority based on business value is very important to defining User Stories. Knowing the value from a story enables us to make good decisions about the sequence of work – building the most important business value components first and getting feedback early rather than trying to build everything at once.
Use Cases are not handled this way and aren’t structured in a way that will easily facilitate planning and prioritization. With use cases, people skilled in writing use cases continue to combine flows and requirements with less regard for the planning and prioritization and with more regard for attempting to create comprehensive system documentation.
Complete vs. Effort-based
A Use Case attempts to completely formalize all of the requirements relating to a particular interaction with the system. User stories are more effort based and less based on levels of precision. The effort to complete a user story is typically one iteration or less. That is at least the goal. Looking at it this way, if a user story is estimated to go beyond a single iteration, it is not a good user story and must be broken down.
User stories aren’t Use cases
User story vs Use case: Both use cases and traditional requirements can be used in agile software development, but they may encourage leaning heavily on documented specification of the system rather than collaboration. Since there is no built-in focus on collaboration, it can be tempting to delve into a detailed specification where the use case becomes the source of record rather than a mechanism for conversations. User stories are more efficient than use cases in Agile and Scrum, as they help remove ambiguity in what your team is delivering by eliciting conversation and collaboration within the delivery team. But there are times when the upfront research that is required for Use Cases is beneficial to the project and should be undertaken.
By themselves, User stories don’t provide the details the team needs to do their work. The Scrum process enables this detail to emerge organically (largely), removing the need to write Use cases. Whether your project requires a User Story, Use Case, or both, depends on the project, the collaboration available, the level of formality, and the upfront research required. Some have found success in a hybrid, such as a highly detailed User Story, while others find the User Story as an important launching off point for the more detailed Use Case. What’s your User story vs Use case project moment? Mention in comments please…