Which of the following is a software testing method that uses an internal perspective of the system to design test cases based on the internal structure?

Waterfall is a sequential software development lifecycle model, not a testing methodology defined by system perspective.

Black box testing evaluates functionality from an external perspective with no knowledge of internal code structure or implementation.

White box testing (also called clear box or structural testing) requires full knowledge of the internal workings of the application under test. Test cases are derived from code paths, branches, loops, and conditions, making it the method that uses an internal perspective of the system to drive test design.

Gray box testing uses partial knowledge of internals combined with external testing techniques, and is not solely based on internal structure.