Which of the following types of testing assesses whether a system works as intended?

Functional testing is focused on verifying that the software functions according to the specified requirements and intended use. This type of testing evaluates the output of the system against its expected outcomes based on the input provided and ensures that all features are operating correctly. It examines each function of the software application by giving appropriate input and checking the output against the expected results, ensuring that the system behaves as intended.

In this context, functional testing assesses whether individual units of code, as well as the entire system, perform their intended tasks effectively. This includes scenarios like user interactions, processing data, and executing functions, which all confirm that the software fulfills the requirements laid out during the design phase.

In contrast, compliance testing would ensure that the system adheres to certain standards or regulations, rather than how it performs in terms of intended functionality. System performance testing evaluates how well the system performs in terms of responsiveness and stability under a specific workload, which is not directly related to functionality. Market viability testing assesses whether the product has a place in the market or potential for success, which does not address the operational integrity of the system itself. Thus, functional testing is the most fitting choice for assessing whether a system works as intended.