You will learn how to write integration tests for reactive Java microservices and to run the tests in true-to-production environments by using containers with Testcontainers and JUnit. Testcontainers tests your containerized application from outside the container so that you are testing the exact same image that runs in production. The reactive application in this guide sends and receives messages between services by using an external message broker, Apache Kafka. Using an external message broker enables asynchronous communications between services so that requests are non-blocking and decoupled from responses. You can learn more about reactive Java services that use an external message broker to manage communications in the Creating reactive Java microservices guide.

Tests sometimes pass during the development and testing stages of an application’s lifecycle but then fail in production because of differences between your development and production environments. While you can create mock objects and custom setups to minimize differences between environments, it is difficult to mimic a production system for an application that uses an external messaging system. Testcontainers addresses this problem by enabling the testing of applications in the same Docker containers that you’ll use in production. As a result, your environment remains the same throughout the application’s lifecycle – from development, through testing, and into production. You can learn more about Testcontainers in the Building true-to-production integration tests with Testcontainers guide.

The Open Liberty Project team