Spring Boot Testing Strategies

Introduction

This sample application made with Spring Boot is intended to show the different approach for testing, from Unit Tests with MockMVC in Standalone mode to full @SpringBootTest as Integration tests between the modules.

The complete guide is available on The Practical Developer Blog.

The application

The logic behind the application is simple: it's a repository of superheroes that you can access through a REST API. It allows to read the available ones (which are hardcoded when the application starts up) and also add new members to the crew.

The architecture is simple: just the Controller layer (REST) and a SuperHeroRepository. To illustrate the differences when creating tests, there are two extra classes that work at a web layer level:

• SuperHeroExceptionHandler. It's a ControllerAdvice that will transform a NonExistingHeroException into a 404 NOT_FOUND HTTP error code.
• SuperHeroFilter. This web filter adds a new header to the HTTP response.

Testing strategies

In the test sources you can find four different approaches to test the Controller. SuperHeroControllerMockMvcStandaloneTest. Uses a MockitoJUnitRunner and it's the most lightweight approach.

Then you can find two approaches using a Spring context, both use MockMVC and one of them already introduces the @SpringBootTest annotation.

Finally, SuperHeroControllerSpringBootTest shows how to write a @SpringBootTest based test mocking other layers but utilizing the web server with a RestTemplate.

To check conclusion and more information please visit the blog.

Changelog

2025/05 Update: Spring Boot 3.4.5 and JDK 24

• The trailing slash in some tests makes them fail. See this blog post
  • Trailing slashes are now removed since they were irrelevant for this blog post
• Moved from javax. packages to jakarta. where needed
• Replaced MockBean's deprecated annotation by its new version MockitoBean