MockMvc for HTTP assertions in Spring Boot - Mini Project: Build & Apply

MockMvc for HTTP assertions

📖 Scenario: You are building a simple Spring Boot web application that has a REST endpoint to greet users by name.To ensure your endpoint works correctly, you want to write tests that simulate HTTP requests and check the responses without starting the full server.

🎯 Goal: Create a test class using MockMvc to send a GET request to the greeting endpoint and assert the HTTP status and response content.

📋 What You'll Learn

Create a Spring Boot REST controller with a GET endpoint /greet that accepts a name query parameter and returns a greeting message.

Set up a MockMvc instance in the test class.

Write a test method that performs a GET request to /greet?name=Alice using MockMvc.

Assert that the HTTP status is 200 (OK) and the response body contains the greeting message Hello, Alice!.

💡 Why This Matters

🌍 Real World

MockMvc is used in Spring Boot projects to test web controllers quickly and reliably without deploying the full application server.

💼 Career

Understanding MockMvc is essential for backend developers working with Spring Boot to write automated tests that ensure web endpoints behave as expected.

1

Create the GreetingController REST endpoint

Create a Spring Boot REST controller class called GreetingController with a GET mapping for /greet that accepts a name query parameter and returns the string "Hello, " + name + "!".

Spring Boot

// Your code here

Need a hint?

Use @RestController and @GetMapping annotations. The method should take a @RequestParam String name and return the greeting string.

2

Set up MockMvc in the test class

Create a test class called GreetingControllerTest annotated with @WebMvcTest(GreetingController.class). Inject a MockMvc field using @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;
import org.junit.jupiter.api.Test;

@WebMvcTest(GreetingController.class)
public class GreetingControllerTest {

    // 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 and assert response

In GreetingControllerTest, write a test method called testGreetReturnsHelloMessage annotated with @Test. Use mockMvc.perform to send a GET request to /greet?name=Alice. Assert that the status is 200 and the response content is exactly Hello, Alice!.

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;

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

Need a hint?

Use mockMvc.perform(get(...)) and chain andExpect calls for status and content.

4

Add @AutoConfigureMockMvc annotation to enable MockMvc auto-configuration

In the GreetingControllerTest class, add the annotation @AutoConfigureMockMvc above the class declaration to enable automatic MockMvc configuration.

Spring Boot

// Add @AutoConfigureMockMvc annotation above the class
@WebMvcTest(GreetingController.class)
public class GreetingControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testGreetReturnsHelloMessage() throws Exception {
        mockMvc.perform(get("/greet?name=Alice"))
            .andExpect(status().isOk())
            .andExpect(content().string("Hello, Alice!"));
    }
}

Need a hint?

Add @AutoConfigureMockMvc above the test class to enable MockMvc auto-configuration.