使用@SpringBootTest进行测试时出现HttpMessageNotWritableException

Question

我试图测试一个基于Spring引导的Restendpoint。代码能够返回预期的输出，但测试失败，错误如下：

已解析[org.springframework.http.converter.HttpMessageNotWritableException:预设内容类型为“null”的[class java.util.LinkedList]没有转换器

对此有任何想法都将不胜感激！

下面是相同的代码：

控制器-

@RestController
public class SampleController {
    
    @Autowired
    StudentService studentService;
    
    @GetMapping(value="students",produces = "application/json")
    public ResponseEntity<List<Student>> getStudentDetails(){
        
    return new ResponseEntity<List<Student>>(studentService.getAllStudents(),HttpStatus.OK);
    }

}

服务等级-

@Service
public class StudentService {
    
    private List<Student> listOfStudents;
    
    @PostConstruct
    public void init() {
        List<Student> list1= new LinkedList<Student>(); 
        Student s1 = new Student("a","S1");
        list1.add(s1);
        listOfStudents = list1;
    }
    
    public List<Student> getAllStudents(){
        return listOfStudents;
    }

}

波乔-

public class Student {

    private String sectionName;
    private String name;
    public String getRollNum() {
        return sectionName;
    }
    public void setRollNum(String rollNum) {
        this.sectionName = rollNum;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Student(String rollNum, String name) {
        this.sectionName = rollNum;
        this.name = name;
    }
    
    @Override
    public String toString() {
        return "Student [sectionName=" + sectionName + ", name=" + name + "]";
    }
    
    
}

试验-

@SpringBootTest(classes = {SampleController.class,StudentService.class})
@AutoConfigureMockMvc
public class SampleControllerTest {

    @Autowired
    private MockMvc mockMvc;
    
    @Autowired
    SampleController sampleController;
    
    @MockBean
    StudentService studentService;
    
    @Test
    public void getAllUsersTest() throws Exception{
        List<Student> mockedList = new LinkedList<Student>();
        Student dummyStudent = new Student("dummy","Dummy Student");
        mockedList.add(dummyStudent);
        Mockito.when(studentService.getAllStudents()).thenReturn(mockedList);
        mockMvc.perform(get("/students")).andExpect(status().isOk());
    }
}

Answer 1

当手动配置@SpringBootTest中的类属性时，springboot的默认自动配置将退出，并且您不会在所有bean中获得springtestcontext:@SpringBootTest（classes={SampleController.class，StudentService.class}）。这样，您的上下文就缺少很多自动配置的bean，比如JSON转换器。

使用@springbootest而不指定类来编写与整个Spring上下文的集成测试，或者使用@WebMvcTest。

我想对于您的测试场景，切片测试注释@WebMvcTest（SampleController.class）就是您要寻找的。这将为您创建一个切片的SpringTestContext，它只包含相关的SpringMVC组件。它还将自动配置MockMvc实例。