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

Functional and structural tests are types of testing techniques that can be applied at various levels of testing. According to the ISTQB CTFL syllabus, functional and structural tests are not restricted to any specific test level but are applicable across all levels of testing. This includes component, integration, system, and acceptance testing. The use of both types of tests helps ensure comprehensive testing coverage, addressing both the functional requirements and the internal structure of the software product​​.