Final answer:
The assumption that the GUI is correctly implemented in test design is false. Test design includes tests to ensure the GUI works as intended, and it's crucial to test thoroughly before finalizing implementation.
Step-by-step explanation:
The assumption that the Graphical User Interface (GUI) has been correctly implemented when conducting test design is false. Instead, test design often includes a variety of tests to verify that the GUI adheres to the specified requirements and functions as intended. When designing tests, one cannot take for granted that any part of the software, including the GUI, is without issues. Testers commonly create and execute tests to locate graphical defects and usability issues before considering the implementation correct.