SpringBootApplication with mock and unit test

HttpRequestTest.java

package com.example.springbootjunitexample;

import com.example.springbootjunitexample.SpringbootJunitExampleApplication.GreetingService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.test.web.servlet.MockMvc;

import static org.assertj.core.api.Assertions.assertThat;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.equalTo;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@WebMvcTest
public class HttpRequestTest {

    @Autowired
    private MockMvc mockMvc;

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

    @MockBean
    private GreetingService service;

    @Test
    public void greetingShouldReturnMessageFromService() throws Exception {
        when(service.greeting()).thenReturn("Hello Mock");
        mockMvc.perform(get("/greeting")).andDo(print())
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello Mock")));
    }

    @Test
    public void helloShouldReturnMessage() throws Exception {
        mockMvc.perform(get("/hello")).andDo(print())
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.a", equalTo("b")));
    }
}

SpringbootJunitExampleApplication.java

package com.example.springbootjunitexample;

import java.util.HashMap;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@SpringBootApplication
public class SpringbootJunitExampleApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootJunitExampleApplication.class, args);
    }


    @org.springframework.stereotype.Controller
    static class Controller {

        @RequestMapping("/")
        @ResponseBody
        public String greeting() {
            return "Hello World";
        }
    }

    @org.springframework.stereotype.Controller
    static class GreetingController {

        private final GreetingService service;

        GreetingController(GreetingService service) {
            this.service = service;
        }

        @GetMapping("/greeting")
        @ResponseBody
        public String greeting() {
            return service.greeting();
        }

        @GetMapping("/hello")
        @ResponseBody
        public HashMap<String, String> hello() {
            return new HashMap<String, String>() {{
                put("a", "b");
            }};
        }
    }

    @Service
    static class GreetingService {

        public String greeting() {
            return "Hello World";
        }
    }
}