Content Type Not Set Junit REST POST test - rest

Question

I have a Spring Boot REST application. The unit tests for all of the GET requests are working perfectly; however, the POST requests are all returning
java.lang.AssertionError: Content type not set
Here is the controller:
#RestController
public class ClassificationController {
private IClassificationService classificationService;
#Autowired
public ClassificationController(IClassificationService classificationService) {
this.classificationService = classificationService;
}
#RequestMapping(value="/category", method = RequestMethod.POST, produces = {MediaType.APPLICATION_JSON_UTF8_VALUE})
#ResponseStatus(HttpStatus.CREATED)
#ResponseBody
public CategoryDTO createCategory(#RequestBody final CategoryDTO category) throws MctException {
return classificationService.createCategory(category);
}
The unit test I have is:
#RunWith(MockitoJUnitRunner.class)
public class ClassificationControllerTest {
#Mock
private IClassificationService classificationService;
#Before
public void setUp() {
mockMvc = MockMvcBuilders.standaloneSetup(new ClassificationController(classificationService)).build();
}
#Test
public void createCategoryTest() throws Exception {
String jsonTask = String.format("{\"id\": \"2\",\"categoryName\": \"Category Name 2\"}");
MvcResult result = mockMvc.perform(post("/category")
.contentType(MediaType.APPLICATION_JSON_UTF8)
.content(jsonTask))
.andDo(MockMvcResultHandlers.print())
.andExpect(content().contentType(MediaType.APPLICATION_JSON_UTF8))
.andExpect(content().string(containsString("\"id\":2")))
.andExpect(content().string(containsString("\"categoryName\":\"Category Name 2\"")))
.andExpect(status().isCreated())
.andReturn();
}
I have also tried this with a CategoryDTO object instead of the String jsonTask with the same result.

Answer 1

I discovered it was just failing on that assertion because it was the first one, but it just wasn't returning anything from the endpoint. I am returning the content type because it is returning the object that is being inserted so a content type is valid. I ended up changing my test create the content JSON using an ObjectMapper and then I had to add an equals method on my domain object....once I added the equals method, the test passed. I didn't realize the mock framework used that method.
#Test
public void createClassTest() throws Exception {
String jsonInString = objectMapper.writeValueAsString(singleClass);
when(classificationService.createClass(5, singleClass)).thenReturn(singleClass);
MvcResult result = mockMvc.perform(post("/class/5")
.contentType(MediaType.APPLICATION_JSON_UTF8)
.content(jsonInString))
.andExpect(content().contentType(MediaType.APPLICATION_JSON_UTF8))
.andExpect(content().string(containsString("\"id\":1")))
.andExpect(content().string(containsString("\"className\":\"Test Class Name 1\"")))
.andExpect(status().isCreated())
.andReturn();
verify(classificationService).createClass(5, singleClass);
}

Answer 2

Judging by the assertion error, it seems the endpoint is not returning a MediaType.APPLICATION_JSON_UTF8. Try removing the contentType check or debugging and seeing what the endpoint is actually returning. Once again, judging by the error you are seeing, seems it's not returning any content type at all. So you should probably be checking that no content type is set.
I know typically the POST request I usually test do not return a contentType at all.
After all, it could be that endpoint is actually doing something incorrectly if you do expect the content type to be set.