MockMvc vs TestRestTemplate: Choosing the Right Tool for Spring Boot Testing

When working with Spring Boot, choosing the right tool for testing your application is crucial. Two popular options for testing the web layer are MockMvc and TestRestTemplate. In this blog post, we’ll explore the differences between MockMvc and TestRestTemplate, helping you decide which is best for your testing needs. 

What is MockMvc? 

MockMvc is a part of the Spring MVC test framework which allows for testing controllers by performing requests and asserting responses without starting a full HTTP server. 

Advantages of MockMvc 

Web Layer Isolation: It focuses solely on the web layer, allowing you to test controllers, JSON serialization, validation, and binding without involving the server, network, or database. 

Detailed Testing: MockMvc provides a detailed inspection and assertion capability of the request and response, useful for fine-grained control over web-behavior. 

Faster Execution: Tests run faster as they only involve the web layer and don’t require an actual server to be up and running. 

Ideal Use Cases for MockMvc

• Unit testing individual controllers.
• Testing specific web layer functionalities like request mappings, form submissions, and validation.
• Situations where detailed assertion of request and response objects is required.

What is TestRestTemplate? 

TestRestTemplate is a template class provided by Spring Boot for integration testing that involves a running server. It is used to make RESTful calls to an actual server and is ideal for full-stack integration testing. 

Advantages of TestRestTemplate 

Full-Stack Testing: TestRestTemplate is used for end-to-end testing of the application, including the web layer, server, and often the database. 

Realistic Scenarios: It is closer to real-world scenarios where the application is running on an actual server, making it ideal for testing the complete stack. 

Ease of Use: It offers a straightforward approach for making REST calls, simplifying the testing of RESTful APIs. 

Ideal Use Cases for TestRestTemplate

• Integration testing where you need to test the application as a whole. 
• Testing RESTful APIs in scenarios that closely mimic the production environment. 
• Situations where you want to test the application's interaction with external services or databases.

Choosing Between MockMvc and TestRestTemplate 

Focus on Web Layer vs. Complete Application: If your focus is solely on the web layer (controller layer) and you need detailed testing of controllers and request mappings, MockMvc is the right choice. For broader integration tests that involve the entire application context, including the web server, TestRestTemplate is more suitable. 

Performance Considerations: For faster test execution focused on the web layer, MockMvc is preferable. If the test speed is less of a concern compared to the breadth of the test, then TestRestTemplate is appropriate. 

Application Type: For microservices or applications where testing individual controllers and their behavior is critical, MockMvc is often the go-to tool. For monolithic applications where end-to-end testing is crucial, TestRestTemplate may be more beneficial. 

Conclusion 

The choice between MockMvc and TestRestTemplate ultimately depends on the specific needs of your testing strategy: 

• Use MockMvc for fast, isolated, and detailed testing of the web layer, especially when you need to focus on unit testing individual components of the web layer. 
• Opt for TestRestTemplate for more comprehensive, end-to-end testing scenarios that require the application to be running more fully, closely replicating the production environment.