Can MySQL Be Used In-Memory for JUnit Testing?

In software development, testing database interactions is essential, but it can require a full-fledged database setup and management. To simplify this process, some developers employ SQLite or H2 databases for in-memory testing. However, is there an option for using MySQL itself in this context?

Solution: MariaDB4j

The answer lies in MariaDB4j, a Gradle/Maven dependency that provides a fully compatible in-memory MySQL database for JUnit testing. It requires minimal setup:

DB database = DB.newEmbeddedDB(3306);
database.start();
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost/test", "root", "");

For additional initialization, a startup script can be included:

database.source("path/to/resource.sql");

Considerations

While MariaDB4j provides an embedded MySQL solution, it does not operate purely in memory. It creates temporary files in the system's temporary folder. As a result, it is not a true in-memory solution, and tests that rely on it may stray from the traditional unit testing definition, which dictates independence from external resources.