How do you test REST endpoints with MockMvc in Spring Boot?

Table of Contents

• Introduction
  • Setting Up MockMvc for Testing
    • 1. Add the Required Dependencies
    • 2. Set Up MockMvc in Your Test Class
    • 3. Write Tests for REST Endpoints
      • Testing a GET Request
      • Testing a POST Request
      • Testing a PUT Request
      • Testing a DELETE Request
    • 4. Verify Response Details
    • Example: Complete Test Class
• Conclusion

Introduction

Testing REST endpoints is a crucial part of ensuring that your Spring Boot application behaves as expected. While unit tests focus on testing isolated components, integration tests verify the interactions between different layers of the application. When testing REST APIs, you can use Spring's MockMvc to simulate HTTP requests and validate responses without starting the full web server. This allows you to test the behavior of controllers and the underlying logic in a fast, efficient manner.

In this guide, we will walk through how to set up and use MockMvc to test REST endpoints in a Spring Boot application.

Setting Up MockMvc for Testing

1. Add the Required Dependencies

Make sure your pom.xml or build.gradle file includes the necessary testing dependencies. For Maven, you can include the spring-boot-starter-test dependency, which includes MockMvc and other essential testing tools.

For Maven:

This starter includes JUnit, Mockito, Hamcrest, and MockMvc, among other testing utilities.

2. Set Up MockMvc in Your Test Class

You need to autowire MockMvc in your test class to perform HTTP requests and validate responses. The easiest way to set it up is by using @WebMvcTest, which configures Spring Boot to load only the web layer (i.e., controllers and related components) for the test.

Explanation of Key Annotations:

• @WebMvcTest: This annotation tells Spring to configure only the web layer (i.e., controllers). It isolates your controller tests and does not load the full application context.

  MockMvc: A mock HTTP request/response object that allows you to simulate HTTP requests and verify responses.

3. Write Tests for REST Endpoints

Once MockMvc is set up, you can begin writing tests for your REST endpoints. Here's a breakdown of how to test different HTTP methods using MockMvc.

Testing a GET Request

To test a GET request, use the get() method and verify the status code and response content:

Testing a POST Request

For testing POST requests, you can use the post() method and send a JSON payload in the request body:

Testing a PUT Request

Testing a PUT request involves sending updated data to an existing resource:

Testing a DELETE Request

To test a DELETE request, simply use delete():

4. Verify Response Details

You can also validate various details in the response:

• Status Code: Use andExpect(status().isOk()) or andExpect(status().isCreated()) to check the HTTP status code.
• Response Body: Use jsonPath() to validate the response body if the response is in JSON format. You can check individual fields or the entire structure.
• Response Headers: If needed, use andExpect(header().string("header-name", "value")) to check specific headers.

Example: Complete Test Class

Conclusion

Testing REST endpoints with MockMvc in Spring Boot provides a simple and effective way to simulate HTTP requests and validate responses without needing a full server environment. By using MockMvc, you can test GET, POST, PUT, and DELETE requests, check the response status, validate the response body, and ensure that your API behaves as expected. This approach helps you maintain robust and reliable API endpoints for your Spring Boot application.

By following the steps outlined above, you can:

• Set up MockMvc in your test class
• Write tests for various HTTP methods (GET, POST, PUT, DELETE)
• Validate response status, body, and headers