ScalaCheck integration

Weaver comes with basic ScalaCheck integration, allowing for property-based testing.

Installation

You'll need to install an additional dependency in order to use ScalaCheck with Weaver.

SBT

libraryDependencies +=  "com.disneystreaming" %% "weaver-scalacheck" % "0.6.15" % Test

Mill

object test extends Tests {
  def ivyDeps = Agg(
    ivy"com.disneystreaming::weaver-scalacheck:0.6.15"
  )
}

Usage

Add the weaver.scalacheck.Checkers mixin to use ScalaCheck within your test suite.

import org.scalacheck.Gen

import weaver._
import weaver.scalacheck._

object ForallExamples extends SimpleIOSuite with Checkers {

  // Using a single `Gen` instance
  test("Single Gen form") {
    // Takes a single, explicit `Gen` instance
    forall(Gen.posNum[Int]) { a =>
      expect(a > 0)
    }
  }

  // There is only one overload for the `forall` that takes an explicit `Gen` parameter
  // To use multiple `Gen` instances, compose them monadically before passing to `forall`
  test("Multiple Gen form") {
    // Compose into a single `Gen[(Int, Int)]`
    val gen = for {
      a <- Gen.posNum[Int]
      b <- Gen.posNum[Int]
    } yield (a, b)

    // Unapply the tuple to access individual members
    forall(gen) { case (a, b) =>
      expect(a > 0) and expect(b > 0)
    }
  }

  // Using a number of `Arbitrary` instances
  test("Arbitrary form") {
    // There are 6 overloads, to pass 1-6 parameters
    forall { (a1: Int, a2: Int, a3: Int) =>
      expect(a1 * a2 * a3 == a3 * a2 * a1)
    }
  }
  
  test("Failure example") {
    // There are 6 overloads, to pass 1-6 parameters
    forall { (a1: Int, a2: Int) =>
      expect(a1 + a2 % 2 == 0)
    }
  }

}

repl.MdocSessionMdocAppForallExamples
+ Single Gen form 314ms
+ Multiple Gen form 323ms
+ Arbitrary form 322ms
- Failure example 70ms
*************FAILURES*************
repl.MdocSessionMdocAppForallExamples
- Failure example 70ms
 [0] Property test failed on try 2 with seed Seed.fromBase64("dTUIQhoDykJIvTU2yMbpdaLm8-lP-oCrUgGJlcw2mRM=") and input (-37029524,-2147483648) (modules/scalacheck/src/weaver/scalacheck/Checkers.scala:194)

 [1] assertion failed (scalacheck.md:53)
 [1] 
 [1] expect(a1 + a2 % 2 == 0)
 [1]        |  | |  |   |
 [1]        |  | |  0   false
 [1]        |  | -2147483648
 [1]        |  -37029524
 [1]        -37029524
Total 4, Failed 1, Passed 3, Ignored 0, Cancelled 0