System Under Test (SUT) When analyzing Web applications, the analysis will typically include the (set of) Web applications themselves, the Web servers and application servers (hardware and software) to be used, the network connections between servers, between clients and servers, and the clients themselves
Component Under Study (CUS) software component of a Web application, or the CPU of the Web server. We could, therefore, abstractly describe
SUT as a set of components, of which a subset has been identified as a CUS