@WebMvcTest for controller testing in JUnit - Test Execution Trace

Test Overview

This test checks a Spring MVC controller using @WebMvcTest. It verifies that a GET request to the controller returns the expected HTTP status and response content.

Test Code - JUnit 5 with Spring Boot Test

JUnit

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

@WebMvcTest(HelloController.class)
public class HelloControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testHelloEndpoint() throws Exception {
        mockMvc.perform(get("/hello"))
               .andExpect(status().isOk())
               .andExpect(content().string("Hello, World!"));
    }
}

// Controller class for reference:
// @RestController
// public class HelloController {
//     @GetMapping("/hello")
//     public String hello() {
//         return "Hello, World!";
//     }
// }

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Spring context loads only the HelloController and related MVC components	Spring Boot test context initialized with HelloController bean and MockMvc configured	-	PASS
2	MockMvc performs a GET request to '/hello' endpoint	Mock HTTP request sent to HelloController's /hello mapping	-	PASS
3	Check that HTTP response status is 200 OK	Response received from controller with status code 200	Assert response status is 200	PASS
4	Check that response body content equals 'Hello, World!'	Response body contains the string 'Hello, World!'	Assert response content string equals 'Hello, World!'	PASS
5	Test completes successfully	Test context remains stable, no errors thrown	-	PASS

Failure Scenario

Failing Condition: The controller does not return the expected string or the endpoint is missing

Execution Trace Quiz - 3 Questions

What does @WebMvcTest do in this test?

A Loads only the web layer including the specified controller

B Loads the entire Spring Boot application context

C Mocks the database layer for testing

D Runs the application on a real server

Key Result

Use @WebMvcTest to isolate controller tests from other layers. This makes tests faster and focused on web behavior only.