Tests for more core functionality - mocking request calls to bridge

[finnkauski]

Is your feature request related to a problem? Please describe. This basically relates to the fact that the bridge as of now is not fully tested because we need to mock request calls to a bridge with our own bridge somehow in order to be able to test.

Describe the solution you'd like This could be implemented in the form of a bridge tester struct that spins up its own thread and listens to requests on a given port and responds with premade json files.