Example of using StringIO

gistfile1.rb

describe 'Your stuff here' do
  context "when doing something fun" do
    it "let's the world know" do
      io = StringIO.new
      logger = Logger.new(io)
      activity = Activity.new(logger: logger)

      expect{ activity.play }.to change{ io.string }.to include "Having so much fun!"
    end
  end
end