I have already written many articles where I was using Docker containers for running some third-party solutions integrated with my sample applications. Building integration tests for such applications may not be an easy task without Docker containers. Especially if our application integrates with databases, message brokers, or some other popular tools. If you are planning to build such integration tests, you should definitely take a look on Testcontainers.
Testcontainers is a Java library that supports JUnit tests, providing a fast and lightweight way for running instances of common databases, Selenium web browsers, or anything else that can run in a Docker container. It provides modules for the most popular relational and NoSQL databases like Postgres, MySQL, Cassandra, or Neo4j. It also allows running popular products like Elasticsearch, Kafka, Nginx, or HashiCorp's Vault. Today, I'm going to show you a more advanced sample of JUnit tests that use Testcontainers to check out an integration between Spring Boot/Spring Cloud application, Postgres database, and Vault.