无法正确应用rest控制器junit测试

@RestController
@RequestMapping("/api")
public class MyController {

    @GetMapping("/hello")
    public String sayHello() {
        return "Hello, World!";
    }
}

import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.test.web.servlet.MockMvc;

@WebMvcTest(MyController.class)
public class MyControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testSayHello() throws Exception {
        mockMvc.perform(get("/api/hello"))
               .andExpect(status().isOk())
               .andExpect(content().string("Hello, World!"));
    }
}