Crafting a Test Case

With everything in place, it’s time to determine what our system will do. We’re talking about an asynchronous message solution. A simple thing to implement would be receiving a request for a new Item object at a web controller and forwarding the information as a message through RabbitMQ. A service would be elsewhere, listening for messages. That service could then write the new Item to MongoDB.

This is a very simple concept we can use over and over. We can also adapt it to our needs. It’s easy to swap out the web controller with something else. Perhaps a message was also transmitted via RabbitMQ. Or, perhaps someone directly invoking the API.

Defining a test class

Let’s return to the initial problem. Namely, a web controller that turns synchronous web requests into asynchronous messages. This time, we’ll choose a test-first approach.

Spring Boot Test, JUnit 5, and Testcontainers put this at our fingertips: