> For the complete documentation index, see [llms.txt](https://ultimatewebsolutions.gitbook.io/qa-knowledge-base/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ultimatewebsolutions.gitbook.io/qa-knowledge-base/test-types/functional-testing.md).

# Functional testing

Checks **what the system does**.

Examples:

* Functional testing
* Smoke testing
* Sanity testing
* Regression testing
* Retesting
* Integration testing
* System testing
* End-to-End (E2E) testing
* User Acceptance Testing (UAT)

Example:

> "When I click Login with valid credentials, I should be logged in."