I just remembered, I fixed this but was waiting for a review. I merged it this morning.

https://github.com/GendronAC/InterSystems-UnitTest-Mocking/pull/3

(code was sent to github per InterSystems request)

Latest code is here : 
https://github.com/GendronAC/InterSystems-UnitTest-Mocking

Let me know if you need something else. Have a look at the CTestCustomPassthroughOperation.cls class

Yes the mocking framework is still under active development here. I'm sorry there are missing classes in the provided example. I'll completely forgot about my reply a year ago...  Yes testing business hosts works very well with it. I'll try to arrange something today and I'll reply here. If I don't, reply back ! 

I am interested !