Continuously develop unit tests

[Bronzila]

In order to ensure, that the mechanics of DEHB function correctly (especially after changes/refactorings), it would be helpful to develop unit tests.

These could be divided into three major categories:

1. DEHB
2. Bracket Manager
3. DE

I would prioritize these test as given by the order of the list above, since DEHB itself and the bracket manager are more likely to be adjusted in the future and therefore the unit tests will act like a safety net to ensure the components still work as they are supposed to.

Depending on which DE implementation we used, there might even be some unit tests in the original repo or did you write the DE code yourself? @Neeratyoy