Introduction - If you have any usage issues, please Google them yourself
MOCK - provides a MOCK Servlet environment, built-in Servlet container and no real start, mainly use @ AutoConfigureMockMvc collocation
RANDOM_PORT - provides a true Servlet environment, that is to say, will start the built-in container, and then using a random port
DEFINED_PORT - this configuration is also offers a real Servlet environment, use the default port, if there is no configuration is 8080
NONE - this is a magical configuration, the same as the Mock also does not provide true Servlet environment.