What is a Use Case?

“Use cases are to software what stories are to novels.” — Unknown

As a software developer or a product manager, writing use cases can be an essential step in the development process to ensure that the software solution meets the needs of its users.

Use cases can help you to understand the requirements of the system by outlining the user’s interaction with the software. They provide an opportunity to explore the functionality of the system and can be used as a communication tool between stakeholders, designers, and developers.

In this guide, we will explore the benefits of writing use cases and provide you with a step-by-step guide to creating effective use cases for your software projects.

A use case is a description of a specific action or interaction between a user (or actor) and a system, which demonstrates the behavior of the system under certain conditions.

It outlines a sequence of steps that represent the user’s interactions with the system in order to achieve a specific goal.

Use cases are often used in software development to help ensure that a system meets the needs of its users and stakeholders.

They provide a clear and detailed understanding of how the system will be used and how it should behave in response to different user actions.

An example use case for a mobile banking application could be a customer wanting to transfer funds from their checking account to their savings account.

The use case would outline the steps the customer takes within the application, such as logging in, navigating to the transfer funds section, selecting the checking account as the source account, selecting the savings account as the destination account, entering the transfer amount, and confirming the transfer.

The use case would also describe any potential errors or exceptions that could occur during the process and how they are handled.

How Do Use Cases Relate to User Stories?

Use cases and user stories are both techniques used in software development to understand user needs and requirements. However, they differ in their level of detail and scope. Use cases are typically more detailed and focus on a specific interaction or task that a user wants to accomplish with the system.

They often include steps, actors, and alternative scenarios. User stories, on the other hand, are brief descriptions of a user’s need or goal that can be used to prioritize and plan development work.

They are often written in a simple, user-centric language and typically do not include the level of detail found in use cases.

In summary, use cases provide a more detailed and structured approach to understanding user requirements, while user stories are a more lightweight and flexible method for capturing user needs.

Both techniques can be useful in different stages of software development and can complement each other in creating a complete understanding of user needs.

What are the Benefits of Use Cases?

There are several benefits of using use cases in software development:

Better understanding of requirements: Use cases provide a clear and concise understanding of the system requirements from a user’s perspective, helping to ensure that the software system meets the user’s needs.
Improved communication: Use cases provide a common language for all stakeholders involved in the software development process, including developers, testers, and business analysts, enabling better communication and collaboration.
Reduced risks and errors: Use cases help to identify potential errors and risks early in the development process, allowing for timely mitigation and reducing the likelihood of costly mistakes.
Improved quality: Use cases provide a clear framework for testing, ensuring that all features and functionalities are thoroughly tested and validated.
Better alignment with business goals: Use cases help to ensure that the software system aligns with the overall business goals and objectives, resulting in software that meets the needs of the business and its users.

What are the Downside of Writing Use Cases?

There are some potential downsides to writing use cases, including:

Time and effort: Writing use cases can be time-consuming and require significant effort, particularly for complex systems or applications.
Lack of flexibility: Use cases are detailed and specific, which can make them less flexible than other requirements gathering techniques like user stories. If the requirements change, the use cases may need to be updated or rewritten.
Focus on functionality over user experience: Use cases tend to focus on the functional requirements of a system, rather than the user experience. This can lead to a system that meets the requirements but is not user-friendly or intuitive.
Potential for confusion: Use cases can be complex and difficult to understand for non-technical stakeholders. This can lead to confusion and misunderstandings, particularly if the use cases are not well-documented or communicated effectively.

Despite these potential downsides, many software development teams find that use cases are a valuable tool for understanding and documenting system requirements, and can help ensure that the final product meets the needs of its users.

How To Write a Use Case

Identify the actors: Begin by identifying the actors involved in the system or process you are describing. Actors are the people, organizations, or systems that interact with your system.
Define the goal: Determine the goal that the actor is trying to achieve by interacting with the system.
List the steps: Break down the process into a series of steps, starting with the initial trigger that sets the process in motion.
Include alternative paths: Identify alternative paths or exceptions that may occur in the process.
Describe the preconditions: Define any preconditions or assumptions that must be met before the use case can be executed.
Identify the post-conditions: Describe what the system or actors are expected to do or receive as a result of completing the use case.
Use clear language: Write the use case in clear and concise language, using language that is easy for all stakeholders to understand.
Review and refine: Once the use case is written, review it with stakeholders to ensure that it accurately reflects the system or process being described. Refine the use case as needed based on feedback.

Example Use Case

For example, a use case for an e-commerce website could be:

Actors: Customer, system administrator

Goal: The customer wants to purchase a product on the website and the system administrator wants to ensure the transaction is successful and the product is shipped.

Steps:

The customer navigates to the product page and selects the product they want to purchase.
The customer adds the product to their cart and proceeds to the checkout page.
The customer enters their payment and shipping information.
The system administrator verifies the payment and shipping information and approves the transaction.
The customer receives a confirmation of the purchase and the system administrator ships the product.

Alternative paths:

If the payment is declined, the customer is notified and given the option to retry the payment or cancel the order.
If the product is out of stock, the customer is notified and given the option to choose a different product or cancel the order.

Preconditions:

The customer has an account on the website.
The product is in stock.

Post-conditions:

The customer’s payment is processed and verified.
The product is shipped to the customer’s specified address.

5 Common Situations for Writing Use Cases

In Writing Effective Use Cases (Agile Software Development, Alistair Cockburn identifies five different situations for writing use cases to help you better understand variances between the purposes and approaches.

Here are the 5 situations:

Eliciting requirements, even if use cases will not be used at all in the final requirements document.
Modeling the business process.
Drafting or sizing system requirements.
Writing functional requirements on a short, high-pressure project.
Writing detailed functional requirements at the start of an increment, on a longer or larger project.

When Should You Write Use Cases?

Use cases should be written during the requirements gathering phase of a software development project. They help to clarify and communicate the functional requirements of the system to stakeholders, including developers, testers, and end-users.

Use cases can also be useful in identifying potential issues or areas of improvement before the development process begins, which can save time and resources in the long run.

Use Cases are a Powerful Tool in Your Toolbox

I think a helpful question to keep any tool or template for use cases on track is to ask, who needs to know what, and what’s the simplest way to share, in a way that’s easy to update or change.

Built to change over built to last. I think the worst mistake is capturing a lot of information that gets in the way of what people really need to know, or that makes it difficult to easily respond to evolving information needs.

Writing effective use cases is a critical step in software development, as it helps ensure that software systems meet user needs and requirements.

By using a structured approach, developers can create use cases that accurately capture the intended functionality of the software system.

While use cases may have their drawbacks, their benefits in terms of improved communication and understanding among stakeholders make them an essential tool in the development process.

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Types of Requirements
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