String Calculator Kata

string_calculator_specs.rb

require "test_notifier/runner/rspec"
TestNotifier.default_notifier = :notify_send

RSpec::Matchers.define :add_to do |expected|
  match do |string|
    string.add == expected
  end
end

module AddableString
  def add
    numbers.inject(0) { |sum, number| sum + number }
  end

  private
    def numbers
      split(any_delimiter).map(&:to_i)
    end

    def any_delimiter
      Regexp.union delimiters
    end

    def delimiters
      return default_delimiters + singlechar_delimiter + bracketed_delimiters
    end

    def default_delimiters
      [",", "\n"]
    end

    def singlechar_delimiter
      has_custom_delimiters?? [self[2]] : []
    end

    def bracketed_delimiters
      scan(/\[(.+?)\]/).map{ |m| m[0] }
    end

    def has_custom_delimiters?
      start_with?("//")
    end
end

class String
  include AddableString
end

describe "String Calculator" do
  it "should return 0 for ''" do
    "".should add_to 0
  end

  context "can add one number" do
    it "should return 1 for 1" do
      "1".should add_to 1
    end

    it "should return 2 for 2" do
      "2".should add_to 2
    end

    it "should return 42 for 42" do
      "42".should add_to 42
    end
  end

  context "can add two numbers" do
    it "should return 2 for 1,1" do
      "1,1".should add_to 2
    end

    it "should return 3 for 1,2" do
      "1,2".should add_to 3
    end

    it "should return 12 for 1,11" do
      "1,11".should add_to 12
    end
  end

  context "can add any amount of numbers" do
    it "should return 6 for 1,2,3" do
      "1,2,3".should add_to 6
    end

    it "should return 200 for one-hundred twos" do
      Array.new(2,100).join(',').should add_to 200
    end
  end

  context "delimiters" do
    it "supports \n as delimiter" do
      "1\n2".should add_to 3
    end

    it "supports ; as delimiter"  do
      "//;\n1;2".should add_to 3
    end

    it "supports % as delimiter" do
      "//%\n1%2".should add_to 3
    end

    context "delimiters of any length" do
      it "supports ;: as delimiter" do
        "//[;:]\n1;:2".should add_to 3
      end

      it "supports ::: as delimiter" do
        "//[:::]\n1:::2".should add_to 3
      end
    end

    context "multiple delimiters" do
      it "supports %, & as delimiters" do
        "//[%][&]\n1%2&3".should add_to 6
      end
    end
  end
end

ahh y quiza podrias reforzar la prueba en el contexto an unknown amount of numbers

Sobre el inject, parece que no funciona sin el (0), ¿puede que porque summand es un string intente inicializar sum="" ? La verdad es que hasta hace 2 días que me lo comentó plagelao no lo conocía. No conozco nada mejor, tampoco me gusta mucho la semántica esa.

Sobre reforzar ese contexto, ¿qué echas en falta?

@xaviuzz el add que proponías devuelve nil en vez de 0 cuando summands == []