gistfile1.rb

require './example'

describe Example do

  it "can mock convert and return the 3rd argument" do
    example = Example.new
    example.stub(:convert)
    example.should_receive(:convert).with(any_args()).and_return { |*args| args[2] }
    result = example.convert('a', 'b', 'c')
    result.should eq('c')
  end

end