Use ScalaCheck generator inside another generator

Question

I have a generator that creates a very compelx object. I cannot create this object through something like

val myGen = for{
 a <- Gen.choose(-10,10)
 ...
} yield new MyClass(a,b,c,...)

I tried an approach of creating a custom generator like this

val myComplexGen :Gen[ComplexObject] = {

  ...
  val myTempVariable = Gen.choose(-10,10)
  val otherTempVal = Gen.choose(100,2000)

  new MyComplexObject(myTempVariable,otherTempVal,...)
}

and then

test("myTest") {
  forAll(myComplexGen){ complexObj => 
        ... // Here, complexObj.myTempVariable is always the same through all the iterations
 }
}

While this works, the values generated are always the same. The inner Gen.choose yield always the same value.

Is there any way I can write a custom Gen with its own logic, and use inner Gen.choose inside, that would be random ?

Answer 1

I've been able to workaround the problem. The solution is definitely not elegant but that's the only way I could work it out.

I have transformed myComplexGen into a def, and called it inside another gen with dummy variables

def myComplexGen :ComplexObject = {

  ...
  val myTempVariable = Gen.choose(-10,10)
  val otherTempVal = Gen.choose(100,2000)

  new MyComplexObject(myTempVariable,otherTempVal,...)
}

---

val realComplexGen :Gen[ComplexObject] = for {
    i <- Gen.choose(0,10) // Not actually used, but for cannot be empty
} yield myComplexGen()

Now I can use realComplexGenin a forAll and the object is really random.