test: reorganize test suite architecture and resolve suite-wide failures - #194

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'db' is assigned a value but never used

'followUtils' is assigned a value but never used

'db' is assigned a value but never used

'next' is defined but never used

'AppError' is assigned a value but never used

'error' is assigned a value but never used

'success' is assigned a value but never used

'engagementService' is assigned a value but never used

'AppError' is assigned a value but never used