In non-functional testing of a safety-critical monitoring system, which aspect would least likely be addressed in the test plan?

In non-functional testing, specific aspects of the system's operation are evaluated, which include attributes like availability, safety, and reliability. These aspects are critical for ensuring that a safety-critical monitoring system meets the necessary requirements to operate effectively under various conditions.

Portability, while an important non-functional aspect in many software systems – referring to the ease with which software can be transferred from one environment to another – is generally less relevant in the context of safety-critical systems. These systems prioritize attributes that ensure safe and consistent operation over different platforms. The focus tends to be much more on how the system can maintain its performance (availability, reliability) and safety under intended operating conditions rather than its ability to be used or adapted in different environments.

Therefore, while portability is important in a broader sense for software testing, it is the aspect least likely to be emphasized in a test plan specifically designed for a safety-critical monitoring system.