RSpec and the Basecamp API

I realise that this is kind of a basic question but I'm new to rspec and still trying to work out how to do things. I'm working on a rails project that requires basecamp integration via the api, which is fairly trivial to use via the basecamp.rb wrapper:

Connection:
basecamp = Basecamp.new(APP_CONFIG['api_host'], APP_CONFIG['api_username'], APP_CONFIG['api_pwd'])

And to retrieve a list of Projects:
puts "Projects: #{basecamp.projects}"

I know how to make this work in the model, I'm just having trouble working out how to create a usable mock for this in rspec. I can't work out to mock 'basecamp.projects' with an object which can then be used in the tests.

Sorry if this is a stupid question but I'm just a bit stuck with it.