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Discover effective techniques to verify that your intended `controllers` are loaded in `WebMvcTest` for Spring Boot Unit Testing. Learn handy methods for new developers!
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How to Check if Your Controllers Are Loaded in WebMvcTest in Spring Boot Unit Tests

When developing applications using Spring Boot, unit testing controller classes is an essential practice. When using the @ WebMvcTest annotation, you might encounter a situation where you have multiple controllers, and you want to ensure that your desired controller is loaded within the testing context. In this guide, we will explore effective methods to verify that your intended controllers are indeed loaded in WebMvcTest scenarios.

Understanding @ WebMvcTest

The @ WebMvcTest annotation is tailored to test Spring MVC components in isolation. It focuses on controller logic and is configured to avoid loading the entire Spring application context, thereby speeding up tests and allowing a clearer focus on web layer testing. However, this specificity can lead to questions regarding how to ensure that particular controllers are present in the context.

How to Verify Loaded Controllers

You can validate that your intended controllers are loaded in the WebMvcTest by following a couple of techniques. Below, we break down these approaches into manageable sections:

Using @ Autowired to Inject Your Controller

One effective way to check if a controller is loaded is through dependency injection using the @ Autowired annotation. Here's a structured example:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Example:

First, we create a simple test class called MyControllerTest and annotate it with @ WebMvcTest(MyController.class), indicating that we want to test MyController specifically.

We use @ Autowired to specify which controllers (and other beans) we want to inject. The required=false parameter allows you to gracefully handle cases where the controller might not be loaded.

Inside our test method, we check:

If otherController is null, it means it wasn't loaded, which is expected.

If myController is not null, then it belongs to the intended loaded controller.

Finally, we use getBean method from WebApplicationContext to further validate the presence of our controllers.

Removing required=false for Assertive Testing

If you want to ensure your tests fail when a controller isn’t present, you can remove the required=false parameter from @ Autowired. The test will naturally fail if the controller cannot be injected. This approach is particularly useful for enforcing the existence of critical controllers in your tests.

Conclusion

Unit testing controllers in Spring Boot using @ WebMvcTest is a powerful technique that can help ensure your application behaves as expected. By using dependency injection and the WebApplicationContext, you can efficiently verify that your intended controllers are loaded correctly. Whether it’s through assertions or adjusting your dependency injection strategy, these methods can improve your testing workflow and catch potential issues early on.

By understanding and implementing these techniques, you can bolster the reliability of your Spring Boot applications and foster confidence in your unit tests. Happy testing!