I am somewhat new to mock objects.  I'm coding up my first one now (in
D) to simulate a "stream" for other objects I want to write.

Even within a single module, I typically have many tests for the methods
within that module.  And since a module's methods make use of each
other, there is again a case for the tests of the lower-level functions
to be executed first.

Anyway, this is something that works for me, but I understand that not
everybody operates this way.

All the best from this Canadian in Switzerland.  :-)