That'll work for our tests, but my only concern is that if this is used in platform, its more ceremony needed for testing I suppose. The current way gives you a nicer wrapping, if it can, but asks nothing of the user. Wrapping adds nothing logically.

If we're less forgiving, then any consumers of this API are also going to have to go through a layer of abstraction (however they choose to do it) if they want to use a mock, or if they want to use something else that doesn't play nicely with `@wraps`.

I haven't written anything that consumes nameko apart from the tests for this PR, so I leave it up to you as to what best fits with the rest of the library...