Shop Manager Implementation

[ev-th]

I'm unsure about the best approach to testing the Application class. My approach was to write unit tests that mocked everything including the Repository classes to test the formatting of the IO, and integration tests to test whether Application was using the Repositories properly.
Mocking the database was time consuming and I'm not sure if it was necessary since the Application class is always initialised only once with the same repository classes, so I'm wondering if rolling the IO formatting testing into the integration tests would have been the best way to go here. Sometimes it feels like I'm going too far with the testing and would like to get a sense of the sweet spot before doing too much and wasting time.
If I had more time, I would have liked to extract some classes out of the Application class since it's getting unwieldy. I would love to get some advice about how to do this, and how to refactor classes like this more generally.