The Twelve Days of Christmas

TwelveDaysOfChristmas.scala

package twelvedays

import scala.annotation.tailrec
class TwelveDays {

  @tailrec
  final def calculateGiftsGivenOnDay(day: Int, totalGifts: Int = 0): Int = {
    if (day == 1) {
      totalGifts + day
    } else {
      calculateGiftsGivenOnDay(day - 1, totalGifts + day)
    }
  }

}

TwelveDaysOfChristmasTests.scala

package zms.GameOfLife

import org.scalatest.Spec
import org.scalatest.matchers.ShouldMatchers
import org.scalatest.junit.JUnitRunner
import org.junit.runner.RunWith

@RunWith(classOf[JUnitRunner])
class GameTests extends Spec with ShouldMatchers {

  describe("all days") {

    it("first day should have 1 gift") {
      val td = new TwelveDays()
      td.calculateGiftsGivenOnDay(1) should be(1)

    }

    it("second day should have 3 gift") {
      val td = new TwelveDays()
      td.calculateGiftsGivenOnDay(2) should be(3)
    }
    it("third day should have 6 gifts") {
    	val td = new TwelveDays()
    	td.calculateGiftsGivenOnDay(3) should be (6)
    }
  }
}