Service & Manager: Add more unit tests

[mihai-stfc]

At the moment, the service is lacking testing for some of the code that has been refactored, while the manager has none.

To-do:

1. Find out what tests would be useful for the service and write them (e.g. DB functions etc.).
2. The manager currently has no tests, try adding unit tests where possible

Notes:

• a coverage checker should help with finding out where there are missing tests

[LowriJenkins]

More testing likely still nesecary so will leave this issue open.
The manager now has much more unit testing, and coverage has been added to the project.
total coverage = approximatly 82%