What is a proper use for Prop.delay in ScalaCheck

Question

Delayed generators could make sense for recursive data structures. I'm wondering in which situation this Prop.delay could be helpful. Could you please demonstrate a real life example.

Answer 1

I'm wondering in which situation this Prop.delay could be helpful. Could you please demonstrate a real life example.

Say you were writing extensions to your property-based test suite in Scalacheck, and wanted the user to build their properties, and your extension expects properties but shouldn't execute them right away.

Actually, Scalacheck uses the Prop.delay construct properties internally to allow users to define tests with the Properties trait/superclass.

class BadExample extends Properties("Bad example") {
  property("divide by 0") = {
    Prop.forAllNoShrink { x: Int =>
      x / 0 == 0 // No!
    }
  }
}

This collects the properties so that they can be executed by a test runner (as an app or through sbt)

sealed class PropertySpecifier() {
  def update(propName: String, p: => Prop) = {
    props += ((name+"."+propName, Prop.delay(p)))
  }
}

private val props = new scala.collection.mutable.ListBuffer[(String,Prop)]

lazy val property = new PropertySpecifier()