Scalacheck arbitrary generators for play-json (https://github.com/playframework/play-json)

arbitrary-play-json.scala

import org.scalacheck._
import play.api.libs.json._

val genJsArray: Gen[JsArray] =
  for {
    n <- Gen.chooseNum(0, 10)
    arr <- Gen.containerOfN[IndexedSeq, JsValue](n, genJsValue).map(JsArray)
  } yield arr

val genJsObject: Gen[JsObject] =
  for {
    n <- Gen.chooseNum(0, 10)
    genKV = for {
      k <- Arbitrary.arbitrary[String]
      v <- genJsValue
    } yield k -> v
    obj <- Gen.buildableOfN[Map[String, JsValue], (String, JsValue)](n, genKV).map(JsObject.apply)
  } yield obj

val genJsValue: Gen[JsValue] = Gen.lzy(Gen.oneOf[JsValue](
  Arbitrary.arbitrary[String].map(JsString),
  Arbitrary.arbitrary[BigDecimal].map(JsNumber),
  Arbitrary.arbitrary[Boolean].map(JsBoolean),
  Gen.const(JsNull),
  genJsArray,
  genJsObject
))