# 4.2.5 Use Case Testing

Tests can be derived from use cases, which are a specific way of designing interactions with software items. They incorporate requirements for the software functions. Use cases are associated with actors (human users, external hardware, or other components or systems) and subjects (the component or system to which the use case is applied).

Each use case specifies some behavior that a subject can perform in collaboration with one or more actors (UML 2.5.1 2017). A use case can be described by interactions and activities, as well as preconditions, postconditions and natural language where appropriate. Interactions between the actors and the subject may result in changes to the state of the subject. Interactions may be represented graphically by work flows, activity diagrams, or business process models.

A use case can include possible variations of its basic behavior, including exceptional behavior and error handling (system response and recovery from programming, application and communication errors, e.g., resulting in an error message). Tests are designed to exercise the defined behaviors (basic, exceptional or alternative, and error handling). Coverage can be measured by the number of use case behaviors tested divided by the total number of use case behaviors, normally expressed as a percentage.

For more information on coverage criteria for use case testing. (see the ISTQB-CTAL-AT).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://magdalenaolak.gitbook.io/istqb-foundation-level/4-test-techniques/4.2-black-box-test-techniques/4.2.5-use-case-testing.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.