start of string calculator kata in ruby

string_calculator_spec.rb

require "rspec"

class StringCalculator

  def add(numbers)
    return 0 if numbers == ""
    return numbers.to_i unless numbers.include? ","
    return numbers[0].to_i + numbers[2].to_i
  end

  def initialize
    puts "initialized!"
  end
end

describe StringCalculator do

  describe ".add" do

    context "empty input" do
      it "should return the default zero" do
        subject.add("").should == 0
      end
    end

    context "single number" do
      it "should return that number" do
       subject.add("1").should == 1
      end
      specify { subject.add("2").should == 2 }
      specify { subject.add("-2").should == -2 }
    end

    context "multiple numbers" do
      it "should sum them up" do
        subject.add("1,2").should == 3
      end
      specify { subject.add("1,3").should == 4}
      specify { subject.add("1,2,3").should == 6}
    end
  end
end