using mocking in [some!] tests

[Robert Collins]

I'm thinking very seriously of using a mocking tool for tests in the
launchpad plugin: its very time consuming to have satisfactory unit
tests without one, and we don't have a 'real alternative
implementation' to automatically test against today anyway - staging
isn't that, for all that its useful for manual interactions.

Any thoughts on this, and/or on selection of a mocking tool? I'd say
Gustavo's mocker, but last I heard he doesn't want it packaged, and I
don't want to add a copy of $whatever to bzr.

-Rob