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giuseppe-trisciuoglio/developer-kit

Comprehensive developer toolkit providing reusable skills for Java/Spring Boot, TypeScript/NestJS/React/Next.js, Python, PHP, AWS CloudFormation, AI/RAG, DevOps, and more.

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troubleshooting.mdplugins/developer-kit-java/skills/unit-test-controller-layer/references/

Troubleshooting Controller Tests

Common Issues and Solutions

Content Type Mismatch

Symptom: 415 Unsupported Media Type error

Solution: Ensure contentType() matches controller's @PostMapping(consumes=...)

// Wrong
mockMvc.perform(post("/api/users").content("{}"));

// Correct
mockMvc.perform(post("/api/users")
    .contentType("application/json")
    .content("{}"));

JsonPath Not Matching

Symptom: JsonPath assertions fail without clear reason

Solution: Use .andDo(print()) to see actual response

mockMvc.perform(get("/api/users/1"))
  .andDo(print())  // Add this to debug
  .andExpect(jsonPath("$.name").value("Alice"));

Status Code Assertions Fail

Symptom: Expected 200 but got 404/500

Solution:

  1. Check controller @RequestMapping paths match test URLs
  2. Verify error handling returns expected status
  3. Ensure service mocks are set up before request
// Verify controller path
@RequestMapping("/api/users")  // Matches "/api/users" not "/users"

// Verify mock setup order
when(userService.getUserById(1L)).thenReturn(user);  // Before perform
mockMvc.perform(get("/api/users/1"))...

Mock Not Being Called

Symptom: verify() fails with "never invoked"

Solution:

  1. Check mock setup happens before perform()
  2. Verify mock parameters match actual call parameters
  3. Use any() for flexible matching
// Use any() for flexible matching
when(userService.createUser(any())).thenReturn(user);
verify(userService).createUser(any());  // Not exact argument

Response Body Empty

Symptom: JsonPath finds nothing in response

Solution:

  1. Verify controller returns response body
  2. Check @ResponseBody or @RestController annotation
  3. Ensure object serialization works
// Controller should return the object
@GetMapping("/{id}")
public UserDto getUser(@PathVariable Long id) {
  return userService.getUserById(id);  // Return, not void
}

ObjectMapper Issues

Symptom: JSON serialization errors or null values

Solution: Configure ObjectMapper in standalone setup

Jackson2ObjectMapperBuilder mapperBuilder = Jackson2ObjectMapperBuilder.json();
mockMvc = MockMvcBuilders.standaloneSetup(controller)
  .setMessageConverters(new MappingJackson2HttpMessageConverter(mapperBuilder.build()))
  .build();

Validation Not Working

Symptom: Validation constraints ignored, 500 instead of 400

Solution: Add validator to standalone setup

@BeforeEach
void setUp() {
  MockitoAnnotations.openMocks(this);
  mockMvc = MockMvcBuilders.standaloneSetup(userController)
    .setValidator(validator)  // Add local validator
    .build();
}

NullPointerException in Controller

Symptom: Tests pass locally but fail in CI

Solution: Ensure all controller dependencies are mocked

@Mock
private UserService userService;

@Mock
private ValidationService validationService;  // Don't forget this one

@InjectMocks
private UserController userController;

plugins

developer-kit-java

skills

unit-test-controller-layer

references

advanced.md

common-pitfalls.md

troubleshooting.md

SKILL.md

README.md

CHANGELOG.md

context7.json

CONTRIBUTING.md

README_CN.md

README_ES.md

README_IT.md

README.md

tessl.json

tile.json