Given the fact that we consider an [explicit use of subject to be a smell](http://blog.davidchelimsky.net/2012/05/13/spec-smell-explicit-use-of-subject/) (it's really just there to support the `it { should }` syntax), I think I'd prefer to see this use the named subject feature:

``` ruby
subject(:invitation) { double('invitation', :deliver => true) }
before { invitation.deliver }
```