The server-side integration tests and unit tests are present in the src/test/java folder.
These can be run directly from the IDE by choosing a package or individual test and running it, or via the command line by running a Gradle test task. Let's run it using the command line. In a new terminal, navigate to the application source folder and execute the following command. It should finish with a success message, as shown here:
> ./gradlew test
...
BUILD SUCCESSFUL in 45s
8 actionable tasks: 6 executed, 2 up-to-date