This section takes socket, which is an important API in the operating system interoperation, as the example to introduce the entire process of test case developing. Considering the length of paper, the test scenario of socket is designed only to verify the ability of establishing connect() between both operating systems, in which one SUT plays the role of client, denoted by OS1, and the other SUT acts as server, denoted by OS2. The entire test scenario is shown in Table 62.1. The verdict on the result is set after executing each step, and it will be set as failure if timeout.