Move all test to test folder + pytest parametrization

[EnricoTrizio]

Up to now, some tests are at the end of the specific files and some are defined in the test folder.

We should move all of them to the test folder and use whenever needed the pytest parametrize functions

[EnricoTrizio]

Maybe we should also remove all the unused prints once we move everything to the test folder or replace them with asserts + intelligible error messages

[EnricoTrizio]

We should also cover in the tests the several checks that we may have that could raise errors
i.e. using pytest.raises

with pytest.raises(ValueError, match='What an horrible error!'):
      some_command_meant_to_raise_an_error()