How to Use H2 as a Test Database in JUnit 5 with Spring Boot

Learn how to easily configure your Spring Boot application to use an in-memory `H2` database for JUnit 5 tests, ensuring a smooth testing experience without dependencies on your production database.
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How to Use H2 as a Test Database in JUnit 5 with Spring Boot

When developing applications in Spring Boot, it's common to use different databases for production and testing. While PostgreSQL is typically used for production environments, using an in-memory database like H2 for tests can greatly enhance your development workflow. However, configuring it correctly can sometimes be tricky. In this guide, we’ll explore a common challenge developers face when trying to set up JUnit 5 tests with H2, and we’ll provide a step-by-step guide to resolve it.

The Challenge

You might encounter issues where your JUnit 5 tests don’t run on a properly configured H2 in-memory database. For instance, in a recent case, a developer noticed that:

They could still access entities from the production database, indicating that the tests were not isolating the test environment correctly.

Even after configuring the properties file, Hibernate continued to use the PostgreSQL dialect instead of switching to H2.

These symptoms suggest that the test configuration was either set up improperly or not being utilized as intended.

Solution Overview

To successfully run your tests on an H2 in-memory database, you may need to follow these steps:

Include H2 Dependency: Ensure that the H2 database is included in your Maven pom.xml file with the correct scope.

Adjust Application Properties: Confirm that your application-test.properties file contains the right settings for H2.

Ensure H2 is Used in Tests: Get rid of unnecessary properties that may interfere with the use of H2.

Let’s delve into each of these steps in detail.

1. Include H2 Dependency in Maven

If you haven't done so already, add the H2 database dependency to your Maven pom.xml. Here’s how you can do it:

[[See Video to Reveal this Text or Code Snippet]]

This inclusion ensures that H2 is only available during testing and doesn’t affect your production build.

2. Configure Application Properties Correctly

Make sure your application-test.properties file is set up correctly. Here’s a recommended configuration:

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Important Note: You might not need the spring.test.database.replace=none property. This line might instruct Spring Boot to avoid replacing the default test database configuration.

3. Verify Your Test Class Configuration

In your test class, make sure to utilize the correct annotations so that the Spring context loads your testing configuration. For instance:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the above steps, you should be able to configure your Spring Boot application to successfully run JUnit 5 tests against an H2 in-memory database. This setup allows for isolated testing scenarios, giving you confidence that your application behaves as expected, independent of the production database.

Say goodbye to database conflicts during your testing phase and embrace the swift, clean solution that H2 provides.

Remember to always check your configuration and dependencies when things aren’t working as expected. Happy coding!

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