When a company decides to create new software, it needs to understand in advance what business and user tasks it will solve and how. To figure this out, a use case (usage scenario) is prepared.
In this article, we will examine what this document is, what tasks it solves, and how to write it correctly.
What is a use case and when is it needed
A use case is a description of how a user interacts with software to achieve a specific goal. It shows what steps a person takes, how the programme responds to them, and what the result is.
For example, a company decides to create an app for ordering taxis. The use case will describe the process of its operation for users — from the main screen to the end of the trip, including feedback. A detailed description allows developers and designers to understand how the system should work and what features need to be implemented.
At the beginning of development, the use case provides a general idea of the software: what is important to the user, what limitations should be taken into account, how exactly the app or website should work, what errors may occur and what to do about them, and much more. Later, these scenarios are used for testing — they are used to check whether the system performs actions as required by users.
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Stages of creating a use case
To write a high-quality use case that is useful in the development and testing stages, you need to go through four consecutive stages: gather information about the software, describe the tasks in the form of a general diagram, detail the scenarios, and plan their verification and refinement if necessary. Let’s take a closer look at each of them.
Gathering information
The key task at the start of work on a use case is to understand the business objectives, i.e. what is important to the customer. This part is usually formulated by a business analyst or product manager. For example, during the information gathering process, it may become clear that there is a need to increase the number of orders, reduce service time or improve customer satisfaction.
Next, we move on to user requirements — what they themselves need from our software: the ability to choose a tariff, quick payment for purchases, or something else. This is where the system analyst or product manager comes in: they interview users, study how they will work with the system, and turn these observations into clear formulations.
Description of the task in the form of a diagram
After analysing the collected data, the systems analyst describes the task as a whole, indicating possible scenarios, but without going into detail. To do this, they use UML — a set of rules for creating visual diagrams. The main advantage of this choice is that the graphic materials will be understandable to anyone familiar with the language. In other words, UML has certain rules for the use of all elements: arrows, circles, squares, and others.
The use case diagram shows all participants in the process and how they interact with the software: actors are depicted as people, the actions themselves are depicted as oval shapes, and the connections between them are represented by arrows and short explanations.
Types of use cases
The same use case can be described both from a business perspective and from the perspective of the system as a whole.
A business scenario shows the task from the perspective of the customer and users. It describes the goal and result without technical details so that it is clear what the business needs. For example: ‘The buyer places an order in an online store: selects a product, pays for it, and receives confirmation.’ It does not specify how the payment system works technically or what code is executed: only the result is important.
The system scenario is intended for developers and testers. It shows what happens inside the software: what checks are implemented and performed, where requests are sent, how the application or website responds to errors. Here is how the wording might look: ‘The system checks the availability of goods in stock, calculates delivery, transfers data to the payment gateway, processes errors, and formats a confirmation letter.’