JavaSpektrum ScalaCheck Example

gistfile1.scala

import org.scalatest.prop.PropertyChecks
import org.scalatest.PropSpec
import org.scalatest.matchers.MustMatchers
import JsonGenerator._
import play.api.libs.json.{Json, JsNumber, JsObject}
import stock.Stock

class StockInfoParserSpec extends PropSpec with PropertyChecks with MustMatchers {

  property("JSON-Werte entsprechen Aktie") {
    forAll { (json: JsObject, last: JsNumber, high: JsNumber, low: JsNumber) =>
        val stockJson = json ++ baseStockData(last, high, low)
        Stock.fromJson(stockJson) must
          be(Stock("ABC", "ABC AG", "EUR", last.value, high.value, low.value))
    }
  }

  property("Nicht valide Kursdaten werden zurückgewiesen") {
    forAll { (last: JsNumber, high: JsNumber, low: JsNumber) =>
      whenever(low.value > last.value && last.value > high.value) {
        val stockJson = baseStockData(last, high, low)
        Stock.validateJson(stockJson) must not be ('defined)
      }
    }
  }

  def baseStockData(last: JsNumber, yearHigh: JsNumber, yearLow: JsNumber) = Json.obj(
    "sym" -> "ABC",
    "name" -> "ABC AG",
    "curr" -> "EUR",
    "last" ->  last,
    "yearHigh" -> yearHigh,
    "yearLow" -> yearLow
  )

}

case class Stock(sym: String, name: String, curr: String, last: BigDecimal, yearHigh : BigDecimal, yearLow: BigDecimal)

object Stock {

  import play.api.libs.json._
  import play.api.libs.functional.syntax._

  implicit val stockRead = (
    (__ \ "sym").read[String] and
      (__ \ "name").read[String] and
      (__ \ "curr").read[String] and
      (__ \ "last").read[BigDecimal] and
      (__ \ "yearHigh").read[BigDecimal] and
      (__ \ "yearLow").read[BigDecimal]
    )(Stock.apply _)

  def fromJson(json: JsObject) = {
    extractJson(json).getOrElse(null)
  }

  def validateJson(json: JsObject) = {
    extractJson(json)
      .filter(stock => stock.last <= stock.yearHigh)
      .filter(stock => stock.last >= stock.yearLow)
      .asOpt
  }

  def extractJson(json: JsObject): JsResult[Stock] = {
    Json.fromJson[Stock](json)
  }
}

import org.scalacheck.{Arbitrary, Gen}
import play.api.libs.json._
import org.scalacheck.Gen._
import play.api.libs.json.JsObject
import play.api.libs.json.JsString
import play.api.libs.json.JsNumber

object JsonGenerator {

  def jsString: Gen[JsString] = for {
    str <- Gen.alphaStr
  } yield JsString(str)

  def jsNumber: Gen[JsNumber] = for {
    decimal <- Gen.chooseNum(0.1, 1000.0)
  } yield JsNumber(decimal)

  def jsTuples: Gen[(String, JsValue)] = for {
    key <- Gen.alphaStr
    v <- oneOf(jsNumber, jsString)
  } yield (key, v)

  def jsObjects: Gen[JsObject] = Gen.sized { size => for {
      amount <- Gen.chooseNum(1, 10)
      elems <- Gen.listOfN(amount, jsTuples)
    } yield JsObject(elems)
  }

  implicit lazy val arbObj: Arbitrary[JsObject] = Arbitrary(jsObjects)
  implicit lazy val arbNum: Arbitrary[JsNumber] = Arbitrary(jsNumber)

}