In user stories, use cases are specific scenarios that detail how a user interacts with a system to achieve a goal. They provide context and clarity for the user story by outlining the steps taken by the user and the system’s responses. Use cases help ensure all potential interactions are considered, facilitating a comprehensive understanding of the requirements. Here are some key elements of use cases in user stories:
- Actor: The user or system interacting with the primary system.
- Goal: The objective the actor wants to achieve.
- Preconditions: Conditions that must be met before the use case starts.
- Main Flow: The sequence of steps taken to achieve the goal.
- Alternate Flows: Variations or exceptions in the main flow.
- Postconditions: The state of the system after the use case is completed.
Use cases provide detailed context to user stories, ensuring all interactions and scenarios are covered.
User Stories, Acceptance Criteria, and Use Cases: Working Together
These three elements work together to define system requirements from a user’s perspective.
- User Stories: A concise description of a feature from the user’s point of view. They typically follow the format “As a [user type], I want [a goal] so that [a benefit].” User stories capture the user’s needs and the reasons behind them.
- Acceptance Criteria: Specific conditions that a user story must meet to be considered complete. Often written as a checklist or “Given-When-Then” scenarios, they define the scope of a user story and serve as a basis for testing.
- Use Cases: Detailed descriptions of how a user interacts with a system to achieve a goal. Use cases include actors (users or systems), preconditions, the main flow of steps, alternative scenarios, and the system’s state after completion. They provide a comprehensive understanding of user interactions and goals.
Combining Acceptance Criteria and Use Cases
- Simple Features: Acceptance criteria might be sufficient, providing clear conditions without needing detailed interaction steps.
- Complex Features: Use cases combined with acceptance criteria ensure all aspects are covered. Acceptance criteria offer clear testing conditions, while use cases detail user interactions.
Choosing the Right Approach
- Team preference: Some prefer the structure of use cases, while others find acceptance criteria more straightforward.
- Project complexity: Complex features benefit from both for thorough understanding.
Example: Adding Items to a Shopping Cart
- User Story: “As an online shopper, I want to add items to my shopping cart so that I can purchase them later.”
- Acceptance Criteria: (Given-When-Then format)
- Adding an item: Shopper logged in, clicks “Add to Cart,” item is added, cart reflects update, confirmation message appears.
- Out-of-stock item: Shopper tries to add unavailable item, “Out of Stock” message displays, item not added.
- Invalid quantity: Shopper enters invalid quantity, error message appears, prompts for valid quantity.
- Use Case:
- Actor: Online shopper
- Goal: Add an item to the cart
- Preconditions: Logged in shopper, available item
- Main Flow: Navigate to product page, select quantity, click “Add to Cart,” system validates availability, adds item to cart, updates cart icon, displays confirmation message.
- Alternate Flows (as specified in Acceptance Criteria)
- Postconditions: Item in cart, updated cart icon, confirmation message displayed.
This combined approach provides a clear and complete picture for development and testing, considering the user’s needs, specific conditions for success, and detailed interaction steps.
