How to write a unit test for a Spring Boot Controller endpoint

Question

I have a sample Spring Boot app with the following

Boot main class

@SpringBootApplication
public class DemoApplication {

    public static void mai         


        

Answer 1

Here is another answer using Spring MVC's standaloneSetup. Using this way you can either autowire the controller class or Mock it.

    import static org.mockito.Mockito.mock;
    import static org.springframework.test.web.server.request.MockMvcRequestBuilders.get;
    import static org.springframework.test.web.server.result.MockMvcResultMatchers.content;
    import static org.springframework.test.web.server.result.MockMvcResultMatchers.status;

    import org.junit.Before;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.test.context.SpringBootTest;
    import org.springframework.http.MediaType;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    import org.springframework.test.web.server.MockMvc;
    import org.springframework.test.web.server.setup.MockMvcBuilders;


    @RunWith(SpringJUnit4ClassRunner.class)
    @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
    public class DemoApplicationTests {

        final String BASE_URL = "http://localhost:8080/";

        @Autowired
        private HelloWorld controllerToTest;

        private MockMvc mockMvc;

        @Before
        public void setup() {
            this.mockMvc = MockMvcBuilders.standaloneSetup(controllerToTest).build();
        }

        @Test
        public void testSayHelloWorld() throws Exception{
            //Mocking Controller
            controllerToTest = mock(HelloWorld.class);

             this.mockMvc.perform(get("/")
                     .accept(MediaType.parseMediaType("application/json;charset=UTF-8")))
                     .andExpect(status().isOk())
                     .andExpect(content().mimeType(MediaType.APPLICATION_JSON));
        }

        @Test
        public void contextLoads() {
        }

    }