Gh-3158: Make use of properties file in Federated Store Tests

[GCHQDeveloper314]

Also tidies up some use of old assertions and blank lines

Related issue

• Resolve #3158

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 66.86%. Comparing base (f6928b3) to head (5dd1cba).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #3218 +/- ## ========================================== Coverage 66.86% 66.86% Complexity 2557 2557 ========================================== Files 912 912 Lines 29276 29276 Branches 3265 3265 ========================================== Hits 19576 19576 Misses 8256 8256 Partials 1444 1444 ```

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