@WebMvcTest for controller testing in Spring Boot - Mini Project: Build & Apply

Testing a Spring Boot Controller with @WebMvcTest

📖 Scenario: You are building a simple Spring Boot web application that has a controller to handle greeting requests. You want to write a test that checks if the controller returns the correct greeting message.

🎯 Goal: Create a Spring Boot test class using @WebMvcTest to test the GreetingController. You will set up the test class, configure the mock MVC, write a test method to perform a GET request, and verify the response.

📋 What You'll Learn

Create a controller class named GreetingController with a GET endpoint /greet that returns a greeting string.

Create a test class annotated with @WebMvcTest(GreetingController.class).

Inject a MockMvc object to perform HTTP requests in the test.

Write a test method that performs a GET request to /greet and asserts the response status is 200 and the content is the expected greeting.

💡 Why This Matters

🌍 Real World

Testing controllers with @WebMvcTest helps ensure your web endpoints behave correctly without starting the full application. This speeds up development and catches bugs early.

💼 Career

Many Java backend developer roles require writing unit and integration tests for Spring Boot applications. Knowing @WebMvcTest is essential for testing web layers efficiently.

1

Create the GreetingController class

Create a Spring Boot controller class named GreetingController with a method greet() mapped to GET requests at /greet. The method should return the string "Hello, Spring!".

Spring Boot

// Create the GreetingController class with a GET endpoint /greet
// Your code here

Need a hint?

Use @RestController on the class and @GetMapping("/greet") on the method.

2

Set up the test class with @WebMvcTest

Create a test class named GreetingControllerTest annotated with @WebMvcTest(GreetingController.class). Inside, declare a private field mockMvc of type MockMvc and annotate it with @Autowired.

Spring Boot

import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.web.servlet.MockMvc;

@WebMvcTest(GreetingController.class)
public class GreetingControllerTest {
    @Autowired
    private MockMvc mockMvc;
    
    // Your code here
}

Need a hint?

Use @WebMvcTest on the test class and @Autowired to inject MockMvc.

3

Write a test method to perform GET request

In the GreetingControllerTest class, write a test method named testGreetReturnsHelloSpring annotated with @Test. Use mockMvc.perform(get("/greet")) to perform a GET request. Then use andExpect(status().isOk()) and andExpect(content().string("Hello, Spring!")) to verify the response status and content.

Spring Boot

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;
import org.junit.jupiter.api.Test;

@WebMvcTest(GreetingController.class)
public class GreetingControllerTest {
    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testGreetReturnsHelloSpring() throws Exception {
        // Your code here
    }
}

Need a hint?

Use mockMvc.perform(get("/greet")) and chain andExpect calls to check status and content.

4

Complete the test class with imports and annotations

Ensure the test class GreetingControllerTest has all necessary imports: @Test from org.junit.jupiter.api.Test, static imports for get, status, and content from MockMvcRequestBuilders and MockMvcResultMatchers. Confirm the class is annotated with @WebMvcTest(GreetingController.class) and the mockMvc field is @Autowired.

Spring Boot

// Review your imports and annotations
// Your code here

Need a hint?

Check that all imports and annotations are present for the test to run correctly.