refactor: scale down tests (#3997)

The test structure and magic for scaling down makes it hard to make any
change. This PR refactor the tests cases in suche way

- only global default mocking
- per test explicit mocking
- per test setup test data, avoiding global data mesh

Test coverage is 100% for scale-down.

Note: Codescene warnings are not new, but a bit the fact of how jest
works

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Co-authored-by: Stuart Pearson <[email protected]>

Author: npalm