Merge Sort in Scala

MergeSort.scala

/**
  * Created by samidarko on 9/20/16.
  */
import util.Random

object MergeSort extends App {

  def merge(left: List[Int], right: List[Int]) : List[Int] = {
    if (left.isEmpty) right
    else if (right.isEmpty) left
    else {
      if (left.head < right.head) left.head :: merge(left.tail, right)
      else right.head :: merge(left, right.tail)
    }
  }

  def mergeSort(l: List[Int]) : List[Int] = {
    if (l.length == 1) l
    else {
      val (left, right) = l.splitAt(l.length/2)
      merge(mergeSort(left), mergeSort(right))
    }
  }

  val l = List(5,3,7,5,8,2,9,1)
  assert(mergeSort(l) == l.sorted)

  val randomList = Seq.fill(6)(Random.nextInt(100)).toList
  assert(mergeSort(randomList) == randomList.sorted)

}