refactor: move test data

[AngryMaciek]

I would strongly suggest to move the test data out of the actual python package directory to a top-lvl dir test. Data live outside of the Python package directory, separated from the source code. The latter should contain only modules/subpackages/submodules.

I see that you use unittest framework. I'm sure it can be adjusted to another repo structure. Since I always use pytest I cannot help more...

Some info:

• https://realpython.com/python-modules-packages/
• https://realpython.com/python-testing/