Scala Language
Testen met ScalaCheck

Invoering

Scalacheck met scalatest en foutmeldingen

Voorbeeld van gebruik scalacheck met scalatest. Hieronder hebben we vier tests:

• "show pass example" - het gaat voorbij
• "toon eenvoudig voorbeeld zonder aangepast foutbericht" - net mislukt bericht zonder details, && boolean operator wordt gebruikt
• "toon voorbeeld met foutmeldingen op argument" - foutmelding op argument ( "argument" |: :) Props.all methode wordt gebruikt in plaats van &&
• "toon voorbeeld met foutmeldingen op opdracht" - foutmelding op opdracht ( "command" |: :) Props.all methode wordt gebruikt in plaats van &&

import org.scalatest.prop.Checkers
import org.scalatest.{Matchers, WordSpecLike}

import org.scalacheck.Gen._
import org.scalacheck.Prop._
import org.scalacheck.Prop

object Splitter {
  def splitLineByColon(message: String): (String, String) = {
    val (command, argument) = message.indexOf(":") match {
      case -1 =>
        (message, "")
      case x: Int =>
        (message.substring(0, x), message.substring(x + 1))
    }
    (command.trim, argument.trim)
  }

  def splitLineByColonWithBugOnCommand(message: String): (String, String) = {
    val (command, argument) = splitLineByColon(message)
    (command.trim + 2, argument.trim)
  }

  def splitLineByColonWithBugOnArgument(message: String): (String, String) = {
    val (command, argument) = splitLineByColon(message)
    (command.trim, argument.trim + 2)
  }
}

class ScalaCheckSpec extends WordSpecLike with Matchers with Checkers {

  private val COMMAND_LENGTH = 4

  "ScalaCheckSpec " should {

    "show pass example" in {
      check {
        Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
          (chars, expArgument) =>
            val expCommand = new String(chars.toArray)
            val line = s"$expCommand:$expArgument"
            val (c, p) = Splitter.splitLineByColon(line)
            Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
        }

      }
    }

"show simple example without custom error message " in {
  check {
    Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
      (chars, expArgument) =>
        val expCommand = new String(chars.toArray)
        val line = s"$expCommand:$expArgument"
        val (c, p) = Splitter.splitLineByColonWithBugOnArgument(line)
        c === expCommand && expArgument === p
    }

  }
}

"show example with error messages on argument" in {
  check {
    Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
      (chars, expArgument) =>
        val expCommand = new String(chars.toArray)
        val line = s"$expCommand:$expArgument"
        val (c, p) = Splitter.splitLineByColonWithBugOnArgument(line)
        Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
    }

  }
}

"show example with error messages on command" in {
  check {
    Prop.forAll(listOfN(COMMAND_LENGTH, alphaChar), alphaStr) {
      (chars, expArgument) =>
        val expCommand = new String(chars.toArray)
        val line = s"$expCommand:$expArgument"
        val (c, p) = Splitter.splitLineByColonWithBugOnCommand(line)
        Prop.all("command" |: c =? expCommand, "argument" |: expArgument =? p)
    }

  }
}

De output (fragmenten):

[info] - should show example // passed
[info] - should show simple example without custom error message  *** FAILED ***
[info]    (ScalaCheckSpec.scala:73)
[info]     Falsified after 0 successful property evaluations.
[info]     Location: (ScalaCheckSpec.scala:73)
[info]     Occurred when passed generated values (
[info]       arg0 = List(), // 3 shrinks
[info]       arg1 = ""
[info]     )
[info] - should show example with error messages on argument *** FAILED ***
[info]    (ScalaCheckSpec.scala:86)
[info]     Falsified after 0 successful property evaluations.
[info]     Location: (ScalaCheckSpec.scala:86)
[info]     Occurred when passed generated values (
[info]       arg0 = List(), // 3 shrinks
[info]       arg1 = ""
[info]     )
[info]     Labels of failing property:
[info]       Expected "" but got "2"
[info]       argument
[info] - should show example with error messages on command *** FAILED ***
[info]    (ScalaCheckSpec.scala:99)
[info]     Falsified after 0 successful property evaluations.
[info]     Location: (ScalaCheckSpec.scala:99)
[info]     Occurred when passed generated values (
[info]       arg0 = List(), // 3 shrinks
[info]       arg1 = ""
[info]     )
[info]     Labels of failing property:
[info]       Expected "2" but got ""
[info]       command