@WebMvcTest for controller testing in JUnit - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple @WebMvcTest controller test

Given the following Spring Boot controller and test, what will be the result of the test execution?

JUnit

import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.web.servlet.MockMvc;
import org.junit.jupiter.api.Test;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@WebMvcTest(HelloController.class)
class HelloControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    void testHelloEndpoint() throws Exception {
        mockMvc.perform(get("/hello"))
               .andExpect(status().isOk());
    }
}

@RestController
class HelloController {
    @GetMapping("/hello")
    public String hello() {
        return "Hello World";
    }
}

A Test passes because the /hello endpoint returns HTTP 200 OK

B Test fails with compilation error due to missing @SpringBootTest annotation

C Test fails with 500 Internal Server Error due to missing service bean

D Test fails with 404 Not Found because the controller is not loaded

💡 Hint

Remember that @WebMvcTest loads only the controller layer and mocks other beans.

@WebMvcTest loads only the specified controller and configures MockMvc for testing web layer. The /hello endpoint exists and returns 200 OK, so the test passes.

❓ assertion

intermediate

Correct assertion to verify JSON response in @WebMvcTest

You have a controller endpoint that returns JSON: {"message":"success"}. Which assertion correctly verifies this JSON response in a @WebMvcTest?

JUnit

mockMvc.perform(get("/api/status"))

A .andExpect(content().string("{message:success}"))

B .andExpect(content().json("{\"message\":\"success\"}"))

C .andExpect(jsonPath("$.message").value("success"))

D .andExpect(status().isOk()).andExpect(content().contentType("text/plain"))

💡 Hint

Use jsonPath to check JSON fields precisely.

jsonPath allows checking specific JSON fields. Option C correctly asserts the message field value. Option C is valid JSON but less precise. Option C is invalid JSON string. Option C checks wrong content type.

🔧 Debug

advanced

Identify cause of 404 error in @WebMvcTest

A @WebMvcTest for a controller returns 404 Not Found when testing the endpoint. Which is the most likely cause?

A The MockMvc bean is not autowired correctly

B The controller class is not included in the @WebMvcTest annotation

C The test method is missing @Test annotation

D The controller method returns null instead of a response

💡 Hint

Check which controllers @WebMvcTest loads.

@WebMvcTest loads only the controllers specified. If the tested controller is not included, the endpoint is not mapped, causing 404.

❓ framework

advanced

Behavior of @WebMvcTest with service layer dependencies

When using @WebMvcTest on a controller that depends on a service bean, what happens if the service bean is not mocked or provided?

A Test passes but service methods are not called

B Test passes because @WebMvcTest automatically mocks all dependencies

C Test fails with NullPointerException inside the controller

D Test fails with NoSuchBeanDefinitionException for the service bean

💡 Hint

Consider what beans @WebMvcTest loads by default.

@WebMvcTest loads only web layer beans. Service beans must be mocked or provided manually. Otherwise, Spring throws NoSuchBeanDefinitionException.

🧠 Conceptual

expert

Purpose and scope of @WebMvcTest in Spring Boot testing

Which statement best describes the purpose and scope of @WebMvcTest in Spring Boot testing?

A @WebMvcTest loads only the web layer components such as controllers, filters, and related configurations for focused controller testing

B @WebMvcTest is used to test repository layer with mock database connections

C @WebMvcTest loads the full application context including database and service layers for integration testing

D @WebMvcTest automatically scans and loads all beans annotated with @Component in the application

💡 Hint

Think about which parts of the app @WebMvcTest focuses on.

@WebMvcTest is designed to test only the web layer, loading controllers and related MVC components, not the full application context.