gistfile1.rb

# Braintree has a cutesy search query API:
class Sweeper
  def self.sweep!
    Braintree::Subscription.search do |s|
      s.status.is Braintree::Subscription::Status::Canceled
    end
  end
end

# Putting expectations on it sucks, but less than I expected:
describe Sweeper do
  it 'searches for canceled subscriptions' do
    Braintree::Subscription.stub(:search) do |block|
      searcher = stub(:status => stub)
      searcher.status.should_receive(:is).
        with(Braintree::Subscription::Status::Canceled)
      block.call(searcher)
    end
    Sweeper.sweep!
  end
end

You could also use rspec's and_yield for this.