Testing rakes with rspec

ruby-talk
1

Hi everyone, I'm having a very strange problem testing some rake tasks with
rspec. I think I'm doing something terribly wrong here, and that's why
rspec is having one of the weirdest behaviours I've ever seen...

Here is one of my rake tasks:

  namespace :rivendell do
    desc 'Outputs the current version of Rivendell'
    task version: :environment do
      puts Rivendell::VERSION
    end
  end

And here is my spec (paths are alright):

  describe 'Rakefile' do
    before :all do
      Rake.application.rake_require '../tasks/rivendell'
      Rake::Task.define_task :environment
    end

    describe 'rivendell::version' do
      # This doesn't appear to work
      let :run_rake_task do
        Rake::Task["rivendell::version"].reenable
        Rake.application.invoke_task "rivendell::version"
      end
      it 'should display the right version' do
        Rivendell.should_receive('VERSION').and_return('0.1')
        run_rake_task
      end
    end
  end

With this version, all tests pass (I invoke it directly with the rspec
command).
The problem is, if I change the should_receive call to
should_receive('sdjkakja') it works as well, this suggests me I'm not
testing my code but some kind of weird double I've created (no idea how,
where or when).
Can someone please help me?

  ngw