Define additional functional tests for FabSim3 and plugins

[djgroen]

Currently, FabSim3 is very thin on functional tests. As part of this ticket, we should add five new functional tests, or incorporate five existing ones on CI. If you have done so, please leave a comment in this ticket referencing the test.

[arabnejad]

@djgroen , test for the replica functionality is added

[djgroen]

That's a good start, containing at least two new CI tests. :)

[djgroen]

I'll move this ticket to M18, so we have a bit more time to establish other ones.

[arabnejad]

Different types of testing are covered by the latest commit
@djgroen do you need more functional tests?

[djgroen]

No, this should be sufficient for M21. Closing this :).