Functional testing describes a testing process used within software development to ensure that all requirements for the application-by-test (AUT) are met. It provides a way to check all functionality, as set out in the specifications (load and performance specification, user story at SCRUM, …).

More simply, the functional testing verifies that every function of a software or application does, such as it is specified in the Technical Requirements (DQRs) or DOD = Definition of Done at SCRUM.

Here, certain inputs are made or operations (use cases or workflows) are performed to compare whether the result or output meets, deviates or eludes the expected result.

Further components of the functional testing are usability tests, navigation and user guidance, input masks, and the behavior of conscious abuse and the resulting errors.

A more detailed article you may find here: Web Application Testing

Prerequisites for functional testing

• Specific requirements include acceptance criteria
• Acceptance criteria are set by the Test Manager or Test engineer.
• SCRUM: User stories are set up with DOD (Definitions of Done). The DODs are converted into test cases

Implementation functional testing

• Themes are structured in test suites
• Test suites contain the individual test cases, which more or less 1: 1 reflect the acceptance criteria in several test steps
• Additionally, use cases or workflows (how a user moves on the site Structure of the regression test cases
• Further test cases

Performing functional testing

• Issue or bug handling
• Documentation
• Issue Management, Release Management