HelloService.java

@Service
public class HelloService {

    public String getHello() {
        return "World";
    }
}

HelloServiceTest.java

@RunWith(SpringRunner.class)
@SpringBootTest
public class HelloServiceTest {

    @Autowired
    private HelloService helloService;

    @Test
    public void shouldReturnCorrectText() {
        assertThat(helloService.getHello()).isEqualTo("World");
    }
}

SimpleController.java

@Controller
public class SimpleController {

    @RequestMapping("/hello")
    @ResponseBody
    public String hello() {
        return "Hello!";
    }
}

SimpleController2.java

@Controller
public class SimpleController {

    @Autowired
    private HelloService helloService;

    @RequestMapping("/hello")
    @ResponseBody
    public String hello() {
        return "Hello!";
    }

    @RequestMapping("/helloworld")
    @ResponseBody
    public String helloWorld() {
        return "Hello " + helloService.getHello() + "!";
    }
}

SimpleControllerTest.java

@RunWith(SpringRunner.class) #1
@WebMvcTest #2
public class SimpleControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void shouldReturnExpectedText() throws Exception {
        mockMvc
                .perform(get("/hello")) #3
                .andExpect(status().isOk()) #4
                .andExpect(content().string(containsString("Hello!"))); #5
    }
}

SimpleControllerTest2.java

@RunWith(SpringRunner.class)
@SpringBootTest #1
@AutoConfigureMockMvc #2
public class SimpleControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void shouldReturnExpectedText() throws Exception {
        mockMvc
                .perform(get("/hello"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello!")));
    }

    @Test
    public void shouldReturnExpectedTextFromService() throws Exception {
        mockMvc
                .perform(get("/helloworld"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello World!"))); 
    }
}

SimpleControllerTest3.java

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
public class SimpleControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private HelloService service; #1

    @Test
    public void shouldReturnExpectedText() throws Exception {
        mockMvc
                .perform(get("/hello"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello!")));
    }



    @Test
    public void shouldReturnExpectedTextFromService() throws Exception {
        when(service.getHello()).thenReturn("Mock"); #2

        mockMvc
                .perform(get("/helloworld"))
                .andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello Mock!"))); #3
    }
}

SpringBootTest.java

.

verify.java

verify(service, times(1)).getHello();