Add datasets tests for FDS

[adam-narozniak]

Issue

Many of the datasets are not tested.

Description

The test would enable checking the integration of the datasets with the FDS library.

Proposal

Mocking datasets to enable the tests of bigger datasets.

Explanation

• New file mock_utils.py contains 1) the code for mocking specific columns 2) the code for mocking specific datasets
• Change and extend the federated_datasets_test.py

Changelog entry

[danieljanes]

The name of mock_utils needs to be changed, otherwise the build system will include it in the final release. Only files ending in _test are excluded.

[adam-narozniak]

I changed the name from mock_utils to mock_utils_test