Using Scalacheck with Inside trait

Question

I have a very simple scenario: test that any pair of random strings of length 10 passed as parameters into a case class Pair(a custom one being under test) should be the same.

class ExercisesPropSpec extends PropSpec with Checkers with Matchers with Inside{

  import Exercises._

  lazy val genPairs = for {
    left <- Gen.listOfN(10, Gen.alphaChar)
    right <- Gen.listOfN(10, Gen.alphaChar)
  } yield (left.mkString, right.mkString)

  property("pattern match tuples of alphanumerics to our custom pair class"){
    forAll(genPairs) {case (left: String, right: String) =>
      val pair = Pair(left, right)
      inside(pair) { case Pair(firstName, lastName) =>
        firstName shouldEqual(left)
        lastName shouldEqual(right)
      }
    }
  }
}

However when I am running testOnly *ExercisesPropSpec from sbt I get this compilation error:

Compiling 1 Scala source to /home/vgorcinschi/ideaProjects/Learning Concurrent Programming in Scala/chapter01_introduction/target/scala-2.12/test-classes ...
[error] ~/ideaProjects/Learning Concurrent Programming in Scala/chapter01_introduction/src/test/scala/org/learningconcurrency/ExercisesPropSpec.scala:18:28: No implicit view available from org.scalatest.Assertion => org.scalacheck.Prop.
[error]     check(forAll(genPairs) {case (left: String, right: String) =>
[error]                            ^

A note in scalacheck-cookbook sais that

what the error message indicates is that our property check is not evaluating in terms of Boolean logic

I was hoping that the inside block in the end should be returning Boolean. I would be grateful if you could point out what am I missing from understanding of property based testing or using Inside trait in this implementation.

Alexey Romanov Alexey Romanov · Accepted Answer · 2018-05-31T05:15:14

You just need to write

firstName == left && lastName == right

instead.

(If shouldEqual did return Boolean, the result of firstName shouldEqual(left) would just be discarded.)

Using Scalacheck with Inside trait

1 Answers