Add scalacheck tests.

lift-json/pom.xml

@@ -21,6 +21,12 @@
       <version>1.5.0</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.scalacheck</groupId>
+      <artifactId>scalacheck</artifactId>
+      <version>1.5</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>

lift-json/src/main/scala/net/liftweb/json/Json.scala

@@ -195,7 +195,7 @@ object JsonDSL extends Printer {
 trait Printer {
   import scala.text._
 
-  def compact(d: Document) = {
+  def compact(d: Document): String = {
     def layout(doc: Document): String = doc match {
       case DocText(s)      => s 
       case DocCons(d1, d2) => layout(d1) + layout(d2)
@@ -207,7 +207,7 @@ trait Printer {
     layout(d)
   }
 
-  def pretty(d: Document) = {
+  def pretty(d: Document): String = {
     val s = new java.io.StringWriter
     d.format(80, s)
     s.toString

lift-json/src/test/scala/net/liftweb/json/Generators.scala

@@ -0,0 +1,24 @@
+package net.liftweb.json
+
+import org.scalacheck._
+import Gen._
+import Arbitrary.arbitrary
+import JsonAST._
+
+trait JValueGen {
+  def genJValue: Gen[JValue] = frequency((5, genSimple), (1, lzy(genArray)), (1, lzy(genObject)))
+  def genSimple: Gen[JValue] = oneOf(
+    value(JNull), 
+    arbitrary[Int].map(JInt(_)),
+    arbitrary[Double].map(JDouble(_)),
+    arbitrary[Boolean].map(JBool(_)),
+    arbitrary[String].map(JString(_)))
+
+  def genArray: Gen[JValue] = for (l <- genList) yield JArray(l)
+  def genObject: Gen[JValue] = for (l <- genFieldList) yield JObject(l)
+
+  def genList = Gen.containerOfN[List, JValue](listSize, genJValue)
+  def genFieldList = Gen.containerOfN[List, JField](listSize, genField)
+  def genField = for (name <- identifier; value <- genJValue) yield JField(name, value)
+  def listSize = choose(0, 5).sample.get
+}

lift-json/src/test/scala/net/liftweb/json/ParserTest.scala

@@ -0,0 +1,22 @@
+package net.liftweb.json
+
+import _root_.org.scalacheck._
+import _root_.org.scalacheck.Prop.forAll
+import _root_.org.specs.Specification
+import _root_.org.specs.runner.{Runner, JUnit}
+import _root_.org.specs.ScalaCheck
+
+class ParserTest extends Runner(ParserSpec) with JUnit
+object ParserSpec extends Specification with JValueGen with ScalaCheck {
+  import JsonAST._
+  import JsonParser._
+
+  "Any valid json" should {
+    "be parseable" in {
+      val parsing = (json: JValue) => parse(JsonDSL.pretty(render(json))).isRight
+      forAll(parsing) must pass
+    }
+  }
+
+  implicit def arbJValue: Arbitrary[JValue] = Arbitrary(genObject)
+}

lift-json/src/test/scala/net/liftweb/json/PrintingTest.scala

@@ -0,0 +1,24 @@
+package net.liftweb.json
+
+import _root_.org.scalacheck._
+import _root_.org.scalacheck.Prop.forAll
+import _root_.org.specs.Specification
+import _root_.org.specs.runner.{Runner, JUnit}
+import _root_.org.specs.ScalaCheck
+
+class PrintingTest extends Runner(PrintingSpec) with JUnit
+object PrintingSpec extends Specification with JValueGen with ScalaCheck {
+  import JsonAST._
+  import scala.text.Document
+
+  "rendering" should {
+    "not change semantics" in {
+      val rendering = (json: Document) => parse(JsonDSL.pretty(json)) == parse(JsonDSL.compact(json))
+      forAll(rendering) must pass
+    }
+  }
+
+  private def parse(json: String) = scala.util.parsing.json.JSON.parse(json)
+
+  implicit def arbDoc: Arbitrary[Document] = Arbitrary(genJValue.map(render(_)))
+}