Which of the following is NOT one of the three elements of system testing?

In the context of system testing, the primary goal is to evaluate the system's functional and non-functional aspects to ensure that it meets specified requirements. The three key elements typically encompass functional testing, non-functional testing, and interface testing.

Functional testing assesses whether the software functions according to the specified requirements. It focuses on the functionalities and behaviors of the application without considering how those functionalities are implemented.

Non-functional testing evaluates aspects of the software that are not related to specific functionalities, such as performance, scalability, usability, and reliability.

Interface testing examines the interactions between different system components, ensuring that communication between them functions as expected.

While security testing is crucial in the overall testing process, it is not categorized under the three primary elements of system testing as outlined in basic testing frameworks. Security testing focuses specifically on identifying vulnerabilities and ensuring that the system's data and resources are protected from attacks, which falls into a separate category of testing. Thus, it does not fit within the main triad of functional, non-functional, and interface testing in the realm of system testing.