When you test applications performing queries on a database, it's not always possible to rely on mocks or embedded databases (e.g. H2): sometimes you need to execute the application in an environment as similar as possible to the production one. In this situations using Docker could be a good idea.
This example shows a Maven project using the docker-maven-plugin for testing a SQL query both on MariaDB and PostgreSQL databases.
During the pre-integration-test phase the plugin starts 2 Docker images (one for MariaDB and one for PostgreSQL).
Inside the src/test/docker directory there are 2 SQL files used to create an example table on both databases. The plugin copies these files in the docker-entrypoint-initdb.d directory inside each Docker image. This directory is used by both images for performing custom initialization.
The plugin is also configured to wait until the databases are up and running (listening on their default ports).
The plugin sets the IP address of the running image inside a Maven property having the following format: docker.container.<image-alias>.ip. In this way it is possible to fill the configuration files inside the src/test/resources directory using Maven properties filtering. Thus, it is possible to read the proper connection configuration from the IntegrationTest class.
Please, have a look to the pom.xml and the other files: there are some additional tips and information contained in the comments.
mvn -Dmaven.failsafe.debug verify