来自端点的模拟响应

Question

我想为此代码创建一个 JUnit 测试：

private Service listsService;
    
    
@RequestMapping(method = {RequestMethod.GET}, path = {"id/{id}"})
    public ResponseEntity<Object> find(@PathVariable String id) {
    
        LookupResponse lookupResponse = listsService.findById(id);
        return new ResponseEntity<>(lookupResponse, HttpStatus.OK);
    }
    
       .................
    
@Override
public LookupResponse findById(String id) {
    
    Optional<Lists> list = ListsRepository.findById(id);
    
    if(list.isPresent())
    {
        Lists lists = binList.get();
        LookupResponse response = LookupResponse.builder()
               .countryCode(lists.getCountry())
                        .category(lists.getType())
                        .build())
               .build();
    
        return response;
    }
    
    return null;
}

我试过这个：

public class ControllerTest {

@MockBean
private ListsService listsService;

@Autowired
private MockMvc mockMvc;

@Test
void justAnExample() {

    LookupResponse lookupResponse = LookupResponse.builder()
            .type("123456")
            .build();

    
   Mockito.when(listsService.findById(Mockito.anyString())).thenReturn(lookupResponse);


}

}

当我运行代码时出现错误：

Cannot invoke "com.ListsService.findById(String)" because "this.listsService" is null
java.lang.NullPointerException: Cannot invoke "com.ListsService.findById(String)" because "this.listsService" is null

你知道我如何正确实施这个模拟测试吗？