Hackibou (09/01/2011) CoffeeScript file - working on the String Calculator kata

string_calculator_spec.coffee

class StringCalculator
  calculate: (input) ->
    @validateArgument(input)

    result = 0
    result += parseInt(splitValue) for splitValue in @splitValues(input)

    result

  validateArgument: (input) ->
    unless (input.match /\n$|,$/) == null
      throw { name: "InvalidArgument", message: "Function argument has invalid character" }

  splitValues: (input) ->
    return input.split(',') if input.indexOf(',') > 0
    input.split '\n'

describe "StringCalculator", ->

  beforeEach ->
    @calculator = new StringCalculator

  describe "with simple cases", ->
    it "returns 1 when the argument is '1'", ->
      (expect @calculator.calculate("1")).toEqual 1

    it "returns 3 when the argument is '3'", ->
      (expect @calculator.calculate("3")).toEqual 3

  describe "with multiple arguments", ->
    it "returns 3 when the argument is '1,2'", ->
      (expect @calculator.calculate("1,2")).toEqual 3

    it "returns 6 when the argument is '1,2,3'", ->
      (expect @calculator.calculate("1,2,3")).toEqual 6

  describe "with different delimiters", ->
    it "returns 3 when the argument is '1\\n,2'", ->
      (expect @calculator.calculate("1,\n2")).toEqual 3

    it "returns 6 when the argument is '1\\n2\\n3'", ->
      (expect @calculator.calculate("1\n2\n3")).toEqual 6

  describe "validating the argument", ->
    it "errors out when called with '1,\\n'", ->
      (expect => @calculator.calculate("1,\n")).toThrow("Function argument has invalid character")

    it "errors out when called with '1,'", ->
      (expect => @calculator.calculate("1,")).toThrow("Function argument has invalid character")