mocha stub for instance variable assignment

Hi,

I'm getting the following error when running spec on my controller:
#<Mock:core>.core_file=(#<Mock:core_file>) - expected calls: 0, actual
calls: 1

This is my mocha rspec setup:
@core = mock('core')
core_file = mock('core_file')
Core.stubs(:new).returns(@core)

And this is the line in my controller on which it fails:
@core.core_file = @core_file

I tried stubbing core_file of @core, but that didn't do anything (e.g.
@core.stubs('core_file').returns(core_file)). And it makes sense,
because in the controller, I assign core_file - I don't access
core_file.

So, the question comes down to: how do I stub instance variable
assignment?

Thanks,
Tiberiu

I got it... @core.stubs(:core_file=).