Add basic integration tests

The project is working but have a very big issue: there is no tests. Everything is tested by hand...

The goal here is to add junit tests to some kind of integration tests with a shieldDB instance with some basic configuration and some shields and check everything works

No files, entry points, or test cases are named. Start by locating the project's JUnit setup and the ShieldDB entry point, then determine how to create an instance with basic configuration and shields; done means basic integration tests exercise that setup and verify the expected behavior.

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