Improve quality of scalacheck range tests input and output.

Remove some dead code, activate ByOne generator again, add generators
for inclusive ranges, add generators that concentrate on the boundaries,
and add some print statements next to exceptions that might get eaten
by out of memory errors.

Author: dcsobral

test/files/scalacheck/range.scala

@@ -12,40 +12,57 @@ class Counter(r: Range) {
     if (cnt % 500000000L == 0L) {
       println("Working: %s %d %d" format (str, cnt, x))
     }
-    if (cnt > (Int.MaxValue.toLong + 1) * 2)
-      error("Count exceeds maximum possible for an Int Range")
-    if ((r.step > 0 && last.exists(_ > x)) || (r.step < 0 && last.exists(_ < x)))
-      error("Range wrapped: %d %s" format (x, last.toString))
+    if (cnt > (Int.MaxValue.toLong + 1) * 2) {
+      val msg = "Count exceeds maximum possible for an Int Range: %s" format str
+      println(msg) // exception is likely to be eaten by an out of memory error
+      sys error msg
+    }
+    if ((r.step > 0 && last.exists(_ > x)) || (r.step < 0 && last.exists(_ < x))) {
+      val msg = "Range %s wrapped: %d %s" format (str, x, last.toString)
+      println(msg) // exception is likely to be eaten by an out of memory error
+      sys error msg
+    }
     last = Some(x)
   }
 }
 
 abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   def myGen: Gen[Range]
 
-  val genRange = for {
-    start <- arbitrary[Int]
-    end <- arbitrary[Int]
-    step <- Gen.choose(1, (start - end).abs + 1)
-  } yield if (start < end) Range(start, end, step) else Range(start, end, -step)
-
-  val genReasonableSizeRange = for {
-    start <- choose(-Int.MinValue, Int.MaxValue)
-    end <- choose(-Int.MinValue, Int.MaxValue)
+  def genReasonableSizeRange = oneOf(genArbitraryRange, genBoundaryRange)
+    
+  def genArbitraryRange = for {
+    start <- choose(Int.MinValue, Int.MaxValue)
+    end <- choose(Int.MinValue, Int.MaxValue)
     step <- choose(-Int.MaxValue, Int.MaxValue)
   } yield Range(start, end, if (step == 0) 100 else step)
 
-  val genSmallRange = for {
+  def genBoundaryRange = for {
+    boundary <- oneOf(Int.MinValue, -1, 0, 1, Int.MaxValue)
+    isStart <- arbitrary[Boolean]
+    size <- choose(1, 100)
+    step <- choose(1, 101)
+  } yield {
+    val signum = if (boundary == 0) 1 else boundary.signum
+    if (isStart) Range(boundary, boundary - size * boundary.signum, - step * signum)
+    else         Range(boundary - size * boundary.signum, boundary, step * signum)
+  }
+
+
+  def genSmallRange = for {
     start <- choose(-100, 100)
     end <- choose(-100, 100)
     step <- choose(1, 1)
   } yield if (start < end) Range(start, end, step) else Range(start, end, -step)
 
-  val genRangeByOne = for {
-    start <- arbitrary[Int]
-    end <- arbitrary[Int]
-    if (end.toLong - start.toLong).abs <= 10000000L
-  } yield if (start < end) Range(start, end) else Range(end, start)
+  def genRangeByOne = oneOf(genRangeOpenByOne, genRangeClosedByOne)
+    
+  def genRangeOpenByOne = for {
+    r <- oneOf(genSmallRange, genBoundaryRange)
+    if (r.end.toLong - r.start.toLong).abs <= 10000000L
+  } yield if (r.start < r.end) Range(r.start, r.end) else Range(r.end, r.start)
+
+  def genRangeClosedByOne = for (r <- genRangeOpenByOne) yield r.start to r.end
 
   def str(r: Range) = "Range["+r.start+", "+r.end+", "+r.step+(if (r.isInclusive) "]" else ")")
 
@@ -71,7 +88,8 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
 
   def multiple(r: Range, x: Int) = (x.toLong - r.start) % r.step == 0
 
-  property("foreach.step") = forAll(myGen) { r =>
+  property("foreach.step") = forAllNoShrink(myGen) { r =>
+//    println("foreach.step "+str(r))
     var allValid = true
     val cnt = new Counter(r)
 //    println("--------------------")
@@ -84,6 +102,7 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   }
 
   property("foreach.inside.range") = forAll(myGen) { r =>
+//    println("foreach.inside.range "+str(r))
     var allValid = true
     var last: Option[Int] = None
     val cnt = new Counter(r)
@@ -94,6 +113,7 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   }
 
   property("foreach.visited.size") = forAll(myGen) { r =>
+//    println("foreach.visited.size "+str(r))
     var visited = 0L
     val cnt = new Counter(r)
     r foreach { x => cnt(x)
@@ -108,14 +128,17 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   }
 
   property("length") = forAll(myGen suchThat (r => expectedSize(r).toInt == expectedSize(r))) { r =>
+//    println("length "+str(r))
     (r.length == expectedSize(r)) :| str(r)
   }
 
   property("isEmpty") = forAll(myGen suchThat (r => expectedSize(r).toInt == expectedSize(r))) { r =>
+//    println("isEmpty "+str(r))
     (r.isEmpty == (expectedSize(r) == 0L)) :| str(r)
   }
 
   property("contains") = forAll(myGen, arbInt.arbitrary) { (r, x) =>
+//    println("contains "+str(r))
 //    println("----------------")
 //    println(str(r))
 //    println(x)
@@ -126,18 +149,21 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   }
 
   property("take") = forAll(myGen suchThat (r => expectedSize(r).toInt == expectedSize(r)), arbInt.arbitrary) { (r, x) =>
+//    println("take "+str(r))
     val t = r take x
     (t.size == (0 max x min r.size) && t.start == r.start && t.step == r.step) :| str(r)+" / "+str(t)+": "+x
   }
 
   property("init") = forAll(myGen suchThat (r => expectedSize(r).toInt == expectedSize(r))) { r =>
+//    println("init "+str(r))
     (r.size == 0) || {
       val t = r.init
       (t.size + 1 == r.size) && (t.isEmpty || t.head == r.head)
     }
   }
 
   property("takeWhile") = forAll(myGen suchThat (r => expectedSize(r).toInt == expectedSize(r)), arbInt.arbitrary) { (r, x) =>
+//    println("takeWhile "+str(r))
     val t = (if (r.step > 0) r takeWhile (_ <= x) else r takeWhile(_ >= x))
     if (r.size == 0) {
       (t.size == 0) :| str(r)+" / "+str(t)+": "+x
@@ -148,6 +174,7 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
   }
 
   property("reverse.toSet.equal") = forAll(myGen) { r =>
+//    println("reverse.toSet.equal "+str(r))
     val reversed = r.reverse
     val aresame = r.toSet == reversed.toSet
     if (!aresame) {
@@ -157,7 +184,7 @@ abstract class RangeTest(kind: String) extends Properties("Range "+kind) {
       println(r.toSet)
       println(reversed.toSet)
     }
-    aresame
+    aresame :| str(r)
   }
 }
 
@@ -178,11 +205,11 @@ object InclusiveRangeTest extends RangeTest("inclusive") {
 }
 
 object ByOneRangeTest extends RangeTest("byOne") {
-  override def myGen = genSmallRange
+  override def myGen = genRangeByOne
 }
 
 object InclusiveByOneRangeTest extends RangeTest("inclusiveByOne") {
-  override def myGen = for (r <- genSmallRange) yield r.inclusive
+  override def myGen = for (r <- genRangeByOne) yield r.inclusive
 }
 
 object SmallValuesRange extends RangeTest("smallValues") {
@@ -207,9 +234,11 @@ object TooLargeRange extends Properties("Too Large Range") {
 object Test extends Properties("Range") {
   import org.scalacheck.{ Test => STest }
 
-  List(NormalRangeTest, InclusiveRangeTest, ByOneRangeTest, InclusiveByOneRangeTest, TooLargeRange) foreach { ps =>
-    STest.checkProperties(STest.Params(testCallback = ConsoleReporter(0)), ps)
-  }
+  include(NormalRangeTest)
+  include(InclusiveRangeTest)
+  include(ByOneRangeTest)
+  include(InclusiveByOneRangeTest)
+  include(TooLargeRange)
 }
 
 /* Mini-benchmark