Let's quickly write a unit test to test the preceding controller method:

    @RunWith(SpringRunner.class)
    @WebMvcTest(BasicController.class)
    public class BasicControllerTest {

      @Autowired
      private MockMvc mvc;

      @Test
      public void welcome() throws Exception {
        mvc.perform(
        MockMvcRequestBuilders.get("/welcome")
       .accept(MediaType.APPLICATION_JSON))
       .andExpect(status().isOk())
       .andExpect(content().string(
       equalTo("Hello World")));
      }
    }

In the preceding unit test, we will launch up a Mock MVC instance with BasicController. A few quick things to note are as follows:

• @RunWith(SpringRunner.class): SpringRunner is a shortcut to the SpringJUnit4ClassRunner annotation. This launches up a simple Spring context for unit testing.
• @WebMvcTest(BasicController.class): This annotation can be used along with SpringRunner to write simple tests for Spring MVC controllers. This will load only the beans annotated with Spring-MVC-related annotations. In this example, we are launching a Web MVC Test context with the class under test being BasicController.
• @Autowired private MockMvc mvc: Autowires the MockMvc bean that can be used to make requests.
• mvc.perform(MockMvcRequestBuilders.get("/welcome").accept(MediaType.APPLICATION_JSON)): Performs a request to /welcome with the Accept header value application/json.
• andExpect(status().isOk()): Expects that the status of the response is 200 (success).
• andExpect(content().string(equalTo("Hello World"))): Expects that the content of the response is equal to "Hello World".