Functional and structural tests are alternative test types that may be used separately or together...

Functional and structural tests are alternative test types that may be used separately or together at B. All test levels. Functional testing is a type of testing that verifies the functionality of the system or component under test against its requirements or specifications. Functional testing focuses on what the system or component does, not how it does it. Structural testing is a type of testing that verifies the structure or code of the system or component under test. Structural testing focuses on how the system or component does it, not what it does. Functional and structural testing can be used separately or together at any test level, such as unit testing, integration testing, system testing, acceptance testing, etc. Functional and structural testing can complement each other by providing different perspectives and coverage of the system or component under test. A detailed explanation of functional and structural testing can be found in [A Study Guide to the ISTQB® Foundation Level 2018 Syllabus], pages 25-26.