Getting random maps from generator code in Scala

I have the following code from the Coursera course Functional Program Design in Scala. It is supposed to be a generator of maps of Int to Int.

lazy val genMap: Gen[Map[Int, Int]] = for {
  k <- arbitrary[Int]
  v <- arbitrary[Int]
  m <- oneOf(const(Map.empty[Int, Int]), genMap)
} yield m.updated(k, v)

My problem is I don't know how to use it. Typing:

genMap.generate

does not work. So how can I get maps from Int to Int from this generator?