[Feature]: Add test mocks for grpc backend

[Slartibartfass2]

To which use case does your feature request relate?

No response

Is your feature request related to a problem? Please describe

Currently, when a gRPC call is used in a test, the error is caught and printed to stderr (as it should be) but sometimes the result is necessary for testing. Therefore, we need to mock those calls to test components that use those calls to the API inside them.

Describe the solution you'd like

Use vitest to mock those calls.

Describe alternatives you've considered

No response

Anything else?

No response