features/step_definitions/foo_steps.rb

require "./calculator"
Given(/^I have (\d+)$/) do |arg1|
	@num = arg1.to_i
end
When(/^I chose to increase it by (\d+)$/) do |arg1|
	puts @num = @num + arg1.to_i
end

Then(/^I should see (\d+)$/) do |arg1|
	if @num != arg1.to_i
		raise "failed"
	end
end