SI-8835 Iterator tests can be junit

Without loss of generality or convenience, but helps
reduce the number of files in test/files and may reduce
compile times for test suite.

This commit includes the fix from #3963 and an extra
test of that fix that ensures the stack doesn't grow
on chained drops.

10 files changed, 167 insertions, 227 deletions

diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 0115cc154c..20712f918c 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -322,8 +322,8 @@ trait Iterator[+A] extends TraversableOnce[A] {
    */
   def drop(n: Int): Iterator[A] = {
     var j = 0
-    while (j < n && this.hasNext) {
-      this.next
+    while (j < n && hasNext) {
+      next()
       j += 1
     }
     this
diff --git a/test/files/run/iterator-concat.check b/test/files/run/iterator-concat.check
deleted file mode 100644
index 23835b07ae..0000000000
--- a/test/files/run/iterator-concat.check
+++ /dev/null
@@ -1,4 +0,0 @@
-100
-1000
-10000
-100000
diff --git a/test/files/run/iterator-concat.scala b/test/files/run/iterator-concat.scala
deleted file mode 100644
index f11363410f..0000000000
--- a/test/files/run/iterator-concat.scala
+++ /dev/null
@@ -1,15 +0,0 @@
-object Test {
-  // Create `size` Function0s, each of which evaluates to an Iterator
-  // which produces 1. Then fold them over ++ to get a single iterator,
-  // which should sum to "size".
-  def mk(size: Int): Iterator[Int] = {
-    val closures = (1 to size).toList.map(x => (() => Iterator(1)))
-    closures.foldLeft(Iterator.empty: Iterator[Int])((res, f) => res ++ f())
-  }
-  def main(args: Array[String]): Unit = {
-    println(mk(100).sum)
-    println(mk(1000).sum)
-    println(mk(10000).sum)
-    println(mk(100000).sum)
-  }
-}
diff --git a/test/files/run/iterator-iterate-lazy.scala b/test/files/run/iterator-iterate-lazy.scala
deleted file mode 100644
index 92b170062e..0000000000
--- a/test/files/run/iterator-iterate-lazy.scala
+++ /dev/null
@@ -1,5 +0,0 @@
-object Test {
-  def main(args: Array[String]): Unit = {
-    Iterator.iterate((1 to 5).toList)(_.tail).takeWhile(_.nonEmpty).map(_.head).toList
-  }
-}
diff --git a/test/files/run/iterators.check b/test/files/run/iterators.check
deleted file mode 100644
index abaf80ff38..0000000000
--- a/test/files/run/iterators.check
+++ /dev/null
@@ -1,14 +0,0 @@
-test check_from was successful
-test check_range was successful
-test check_range2 was successful
-test check_range3 was successful
-test check_take was successful
-test check_drop was successful
-test check_slice was successful
-test check_foreach was successful
-test check_forall was successful
-test check_fromArray was successful
-test check_toSeq was successful
-test check_indexOf was successful
-test check_findIndexOf was successful
-
diff --git a/test/files/run/iterators.scala b/test/files/run/iterators.scala
deleted file mode 100644
index d54da3d3ba..0000000000
--- a/test/files/run/iterators.scala
+++ /dev/null
@@ -1,168 +0,0 @@
-//############################################################################
-// Iterators
-//############################################################################
-
-//############################################################################
-
-import scala.language.postfixOps
-
-object Test {
-
-  def check_from: Int = {
-    val it1 = Iterator.from(-1)
-    val it2 = Iterator.from(0, -1)
-    it1.next + it2.next
-  }
-
-  def check_range: Int = {
-    val xs1 = Iterator.range(0, 10,  2) toList;
-    val xs2 = Iterator.range(0, 10, -2) toList;
-    val xs3 = Iterator.range(10, 0, -2) toList;
-    val xs4 = Iterator.range(10, 0,  2) toList;
-    val xs5 = Iterator.range(0, 10, 11) toList;
-    xs1.length + xs2.length + xs3.length + xs4.length + xs5.length
-  }
-
-  def check_range2: Int = {
-    val r1start = 0
-    val r1end = 10
-    val r1step = 1
-    val r1 = Iterator.range(r1start, r1end, r1step) toList;
-    val r2 = Iterator.range(r1start, r1end, r1step + 1) toList;
-    val r3 = Iterator.range(r1end, r1start, -r1step) toList;
-    val r4 = Iterator.range(0, 10, 11) toList;
-    // 10 + 5 + 10 + 1
-    r1.length + r2.length + r3.length + r4.length
-  }
-
-  def check_range3: Int = {
-    def trues(xs: List[Boolean]) = xs.foldLeft(0)((a, b) => if (b) a+1 else a)
-    val r1 = Iterator.range(0, 10)
-    val xs1 = List(r1 contains 5, r1 contains 6)
-    val r2a = Iterator.range(0, 10, 2)
-    val r2b = Iterator.range(0, 10, 2)
-    val xs2 = List(r2a contains 5, r2b contains 6)
-    val r3 = Iterator.range(0, 10, 11)
-    val xs3 = List(r3 contains 5, r3 contains 6)
-    // 2 + 1 + 0
-    trues(xs1) + trues(xs2) + trues(xs3)
-  }
-
-  def check_take: Int = {
-    val it1 = Iterator.from(0)
-    val xs1 = it1 take 10 toList;
-    xs1.length
-  }
-
-  def check_drop: Int = {
-    val tests = Array(
-      Iterator.from(0).take(5).drop(1).toSeq sameElements Seq(1, 2, 3, 4),
-      Iterator.from(0).take(5).drop(3).toSeq sameElements Seq(3, 4),
-
-      Iterator.from(0).take(5).drop(5).toSeq sameElements Seq(),
-      Iterator.from(0).take(5).drop(10).toSeq sameElements Seq(),
-
-      Iterator.from(0).take(5).drop(0).toSeq sameElements Seq(0, 1, 2, 3, 4),
-      Iterator.from(0).take(5).drop(-1).toSeq sameElements Seq(0, 1, 2, 3, 4),
-
-      Iterator.from(0).take(5).drop(1).map(2 * _).toSeq sameElements Seq(2, 4, 6, 8),
-      Iterator.from(0).take(5).map(2 * _).drop(1).toSeq sameElements Seq(2, 4, 6, 8),
-
-      Iterator.from(0).take(5).drop(1).drop(2).toSeq sameElements Seq(3, 4),
-      Iterator.from(0).take(5).drop(2).drop(1).toSeq sameElements Seq(3, 4)
-    )
-    tests.count(result => result)
-  }
-
-  def check_slice: Int = {
-    val tests = Array(
-      Iterator.from(0).slice(3, 7).toSeq sameElements Seq(3, 4, 5, 6),
-      Iterator.from(0).slice(3, 3).toSeq sameElements Seq(),
-      Iterator.from(0).slice(-1, 3).toSeq sameElements Seq(0, 1, 2),
-      Iterator.from(0).slice(3, -1).toSeq sameElements Seq(),
-
-      Iterator.from(0).slice(3, 7).map(2 * _).toSeq sameElements Seq(6, 8, 10, 12),
-      Iterator.from(0).map(2 * _).slice(3, 7).toSeq sameElements Seq(6, 8, 10, 12),
-
-      Iterator.from(0).slice(3, 7).drop(1).toSeq sameElements Seq(4, 5, 6),
-      Iterator.from(0).drop(1).slice(3, 7).toSeq sameElements Seq(4, 5, 6, 7),
-
-      Iterator.from(0).slice(3, 7).slice(1, 3).toSeq sameElements Seq(4, 5),
-      Iterator.from(0).slice(3, 7).slice(1, 10).toSeq sameElements Seq(4, 5, 6)
-    )
-    tests.count(result => result)
-  }
-
-  def check_foreach: Int = {
-    val it1 = Iterator.from(0) take 20
-    var n = 0
-    it1 foreach { n += _ }
-    n
-  }
-
-  def check_forall: Int = {
-    val it1 = Iterator.from(0)
-    val it2 = Iterator.from(1)
-    0
-  }
-
-  def check_fromArray: Int = {  // ticket #429
-    val a = List(1, 2, 3, 4).toArray
-    var xs0 = a.iterator.toList;
-    var xs1 = a.slice(0, 1).iterator.toList;
-    var xs2 = a.slice(0, 2).iterator.toList;
-    var xs3 = a.slice(0, 3).iterator.toList;
-    var xs4 = a.slice(0, 4).iterator.toList;
-    xs0.length + xs1.length + xs2.length + xs3.length + xs4.length
-  }
-
-  def check_toSeq: String =
-    List(1, 2, 3, 4, 5).iterator.toSeq.mkString("x")
-
-  def check_indexOf: String = {
-    val i = List(1, 2, 3, 4, 5).indexOf(4)
-    val j = List(1, 2, 3, 4, 5).indexOf(16)
-    "" + i + "x" + j
-  }
-
-  def check_findIndexOf: String = {
-    val i = List(1, 2, 3, 4, 5).indexWhere { x: Int => x >= 4 }
-    val j = List(1, 2, 3, 4, 5).indexWhere { x: Int => x >= 16 }
-    "" + i + "x" + j
-  }
-
-  def check_success[A](name: String, closure: => A, expected: A) {
-    print("test " + name)
-    try {
-      val actual: A = closure
-      if (actual == expected)
-        print(" was successful")
-      else
-        print(" failed: expected "+ expected +", found "+ actual)
-    }
-    catch {
-      case exception: Throwable =>
-        print(" raised exception " + exception)
-    }
-    println()
-  }
-
-  def main(args: Array[String]) {
-    check_success("check_from",     check_from,      -1)
-    check_success("check_range",    check_range,     11)
-    check_success("check_range2",   check_range2,    26)
-    check_success("check_range3",   check_range3,     3)
-    check_success("check_take",     check_take,      10)
-    check_success("check_drop",     check_drop,      10)
-    check_success("check_slice",    check_slice,     10)
-    check_success("check_foreach",  check_foreach,  190)
-    check_success("check_forall",   check_forall,     0)
-    check_success("check_fromArray",check_fromArray, 14)
-    check_success("check_toSeq",  check_toSeq, "1x2x3x4x5")
-    check_success("check_indexOf",     check_indexOf,     "3x-1")
-    check_success("check_findIndexOf", check_findIndexOf, "3x-1")
-    println()
-  }
-}
-
-//############################################################################
diff --git a/test/files/run/t3516.check b/test/files/run/t3516.check
deleted file mode 100644
index d0d10d82fa..0000000000
--- a/test/files/run/t3516.check
+++ /dev/null
@@ -1,3 +0,0 @@
-1
-1
-21
diff --git a/test/files/run/t3516.scala b/test/files/run/t3516.scala
deleted file mode 100644
index aa302ce85a..0000000000
--- a/test/files/run/t3516.scala
+++ /dev/null
@@ -1,13 +0,0 @@
-object Test {
-  def mkIterator = (1 to 5).iterator map (x => { println(x) ; x })
-  def mkInfinite = Iterator continually { println(1) ; 1 }
-
-  def main(args: Array[String]): Unit = {
-    // Stream is strict in its head so we should see 1 from each of them.
-    val s1 = mkIterator.toStream
-    val s2 = mkInfinite.toStream
-    // back and forth without slipping into nontermination.
-    println((Stream from 1).toIterator.drop(10).toStream.drop(10).toIterator.next)
-    ()
-  }
-}
diff --git a/test/junit/scala/collection/IteratorTest.scala b/test/junit/scala/collection/IteratorTest.scala
index b7a9805c9f..04af074ac7 100644
--- a/test/junit/scala/collection/IteratorTest.scala
+++ b/test/junit/scala/collection/IteratorTest.scala
@@ -6,11 +6,12 @@ import org.junit.Test
 import org.junit.runner.RunWith
 import org.junit.runners.JUnit4
 
+import scala.tools.testing.AssertUtil._
+
 @RunWith(classOf[JUnit4])
 class IteratorTest {
 
-  @Test
-  def groupedIteratorShouldNotAskForUnneededElement(): Unit = {
+  @Test def groupedIteratorShouldNotAskForUnneededElement(): Unit = {
     var counter = 0
     val it = new Iterator[Int] { var i = 0 ; def hasNext = { counter = i; true } ; def next = { i += 1; i } }
     val slidingIt = it sliding 2
@@ -25,4 +26,147 @@ class IteratorTest {
     slidingIt.next
     assertEquals("Counter should be one, that means we didn't look further than needed", 1, counter)
   }
+
+  @Test def dropDoesNotGrowStack(): Unit = {
+    def it = new Iterator[Throwable] { def hasNext = true ; def next = new Throwable }
+
+    assertEquals(it.drop(1).next.getStackTrace.length, it.drop(1).drop(1).next.getStackTrace.length)
+  }
+
+  @Test def dropIsChainable(): Unit = {
+    assertSameElements(1 to 4, Iterator.from(0).take(5).drop(1).toList)
+    assertSameElements(3 to 4, Iterator.from(0).take(5).drop(3).toList)
+    assertSameElements(Seq.empty, Iterator.from(0).take(5).drop(5).toList)
+    assertSameElements(Seq.empty, Iterator.from(0).take(5).drop(10).toList)
+    assertSameElements(0 to 4, Iterator.from(0).take(5).drop(0).toList)
+    assertSameElements(0 to 4, Iterator.from(0).take(5).drop(-1).toList)
+    assertSameElements(2 to 8 by 2, (Iterator from 0 take 5 drop 1 map (2 * _)).toList)
+    assertSameElements(2 to 8 by 2, (Iterator from 0 take 5 map (2 * _) drop 1).toList)
+    assertSameElements(3 to 4, (Iterator from 0 take 5 drop 1 drop 2).toList)
+    assertSameElements(3 to 4, (Iterator from 0 take 5 drop 2 drop 1).toList)
+  }
+
+  @Test def sliceIsChainable(): Unit = {
+    assertSameElements(3 to 6, Iterator from 0 slice (3, 7))
+    assertSameElements(Seq.empty, Iterator from 0 slice (3, 3))
+    assertSameElements(0 to 2, Iterator from 0 slice (-1, 3))
+    assertSameElements(Seq.empty, Iterator from 0 slice (3, -1))
+    assertSameElements(6 to 12 by 2, Iterator from 0 slice (3, 7) map (2 * _))
+    assertSameElements(6 to 12 by 2, Iterator from 0 map (2 * _) slice (3, 7))
+    assertSameElements(4 to 6, Iterator from 0 slice (3, 7) drop 1)
+    assertSameElements(4 to 7, Iterator from 0 drop 1 slice (3, 7))
+    assertSameElements(4 to 5, Iterator from 0 slice (3, 7) slice (1, 3))
+    assertSameElements(4 to 6, Iterator from 0 slice (3, 7) slice (1, 10))
+  }
+
+  // test/files/run/iterator-concat.scala
+  @Test def concatIsStackFriendly(): Unit = {
+    // Create `size` Function0s, each of which evaluates to an Iterator
+    // which produces 1. Then fold them over ++ to get a single iterator,
+    // which should sum to "size".
+    def mk(size: Int): Iterator[Int] = {
+      //val closures = (1 to size).toList.map(x => (() => Iterator(1)))
+      //closures.foldLeft(Iterator.empty: Iterator[Int])((res, f) => res ++ f())
+      List.fill(size)(() => Iterator(1)).foldLeft(Iterator.empty: Iterator[Int])((res, f) => res ++ f())
+    }
+    assertEquals(100,    mk(100).sum)
+    assertEquals(1000,   mk(1000).sum)
+    assertEquals(10000,  mk(10000).sum)
+    assertEquals(100000, mk(100000).sum)
+  }
+
+  @Test def from(): Unit = {
+    val it1 = Iterator.from(-1)
+    val it2 = Iterator.from(0, -1)
+    assertEquals(-1, it1.next() + it2.next())
+  }
+  @Test def range(): Unit = {
+    val xs1 = Iterator.range(0, 10,  2)
+    val xs2 = Iterator.range(0, 10, -2)
+    val xs3 = Iterator.range(10, 0, -2)
+    val xs4 = Iterator.range(10, 0,  2)
+    val xs5 = Iterator.range(0, 10, 11)
+    assertEquals(11, xs1.size + xs2.size + xs3.size + xs4.size + xs5.size)
+  }
+  @Test def range2(): Unit = {
+    val r1start = 0
+    val r1end = 10
+    val r1step = 1
+    val r1 = Iterator.range(r1start, r1end, r1step)
+    val r2 = Iterator.range(r1start, r1end, r1step + 1)
+    val r3 = Iterator.range(r1end, r1start, -r1step)
+    val r4 = Iterator.range(0, 10, 11)
+    // 10 + 5 + 10 + 1
+    assertEquals(10 + 5 + 10 + 1, r1.size + r2.size + r3.size + r4.size)
+  }
+  @Test def range3(): Unit = {
+    def trues(xs: List[Boolean]) = xs.foldLeft(0)((a, b) => if (b) a+1 else a)
+    val r1 = Iterator.range(0, 10)
+    val xs1 = List(r1 contains 5, r1 contains 6)
+    val r2a = Iterator.range(0, 10, 2)
+    val r2b = Iterator.range(0, 10, 2)
+    val xs2 = List(r2a contains 5, r2b contains 6)
+    val r3 = Iterator.range(0, 10, 11)
+    val xs3 = List(r3 contains 5, r3 contains 6)
+    // 2 + 1 + 0
+    assertEquals(2 + 1 + 0, trues(xs1) + trues(xs2) + trues(xs3))
+  }
+  @Test def take(): Unit = {
+    val it1 = Iterator.from(0)
+    val xs1 = it1 take 10
+    assertEquals(10, xs1.size)
+  }
+  @Test def foreach(): Unit = {
+    val it1 = Iterator.from(0) take 20
+    var n = 0
+    it1 foreach { n += _ }
+    assertEquals(190, n)
+  }
+  /* ???
+  @Test def forall(): Unit = {
+    val it1 = Iterator.from(0)
+    val it2 = Iterator.from(1)
+    0
+  }
+  */
+  // ticket #429
+  @Test def fromArray(): Unit = {
+    val a = List(1, 2, 3, 4).toArray
+    var xs0 = a.iterator.toList;
+    var xs1 = a.slice(0, 1).iterator
+    var xs2 = a.slice(0, 2).iterator
+    var xs3 = a.slice(0, 3).iterator
+    var xs4 = a.slice(0, 4).iterator
+    assertEquals(14, xs0.size + xs1.size + xs2.size + xs3.size + xs4.size)
+  }
+  @Test def toSeq(): Unit = {
+    assertEquals("1x2x3x4x5", List(1, 2, 3, 4, 5).iterator.mkString("x"))
+  }
+  @Test def indexOf(): Unit = {
+    assertEquals(3, List(1, 2, 3, 4, 5).indexOf(4))
+    assertEquals(-1, List(1, 2, 3, 4, 5).indexOf(16))
+  }
+  @Test def indexWhere(): Unit = {
+    assertEquals(3, List(1, 2, 3, 4, 5).indexWhere { x: Int => x >= 4 })
+    assertEquals(-1, List(1, 2, 3, 4, 5).indexWhere { x: Int => x >= 16 })
+  }
+  // iterator-iterate-lazy.scala
+  // was java.lang.UnsupportedOperationException: tail of empty list
+  @Test def iterateIsSufficientlyLazy(): Unit = {
+    //Iterator.iterate((1 to 5).toList)(_.tail).takeWhile(_.nonEmpty).toList  // suffices
+    Iterator.iterate((1 to 5).toList)(_.tail).takeWhile(_.nonEmpty).map(_.head).toList
+  }
+  // SI-3516
+  @Test def toStreamIsSufficientlyLazy(): Unit = {
+    val results = collection.mutable.ListBuffer.empty[Int]
+    def mkIterator = (1 to 5).iterator map (x => { results += x ; x })
+    def mkInfinite = Iterator continually { results += 1 ; 1 }
+
+    // Stream is strict in its head so we should see 1 from each of them.
+    val s1 = mkIterator.toStream
+    val s2 = mkInfinite.toStream
+    // back and forth without slipping into nontermination.
+    results += (Stream from 1).toIterator.drop(10).toStream.drop(10).toIterator.next()
+    assertSameElements(List(1,1,21), results)
+  }
 }
diff --git a/test/junit/scala/tools/testing/AssertUtil.scala b/test/junit/scala/tools/testing/AssertUtil.scala
index 9b4833d46b..83a637783f 100644
--- a/test/junit/scala/tools/testing/AssertUtil.scala
+++ b/test/junit/scala/tools/testing/AssertUtil.scala
@@ -1,6 +1,11 @@
 package scala.tools
 package testing
 
+import org.junit.Assert
+import Assert.fail
+import scala.runtime.ScalaRunTime.stringOf
+import scala.collection.{ GenIterable, IterableLike }
+
 /** This module contains additional higher-level assert statements
  *  that are ultimately based on junit.Assert primitives.
  */
@@ -21,6 +26,19 @@ object AssertUtil {
           throw e
         else return
     }
-    throw new AssertionError("Expression did not throw!")
+    fail("Expression did not throw!")
   }
+
+  /** JUnit-style assertion for `IterableLike.sameElements`.
+   */
+  def assertSameElements[A, B >: A](expected: IterableLike[A, _], actual: GenIterable[B], message: String = ""): Unit =
+    if (!(expected sameElements actual))
+      fail(
+        f"${ if (message.nonEmpty) s"$message " else "" }expected:<${ stringOf(expected) }> but was:<${ stringOf(actual) }>"
+      )
+
+  /** Convenient for testing iterators.
+   */
+  def assertSameElements[A, B >: A](expected: IterableLike[A, _], actual: Iterator[B]): Unit =
+    assertSameElements(expected, actual.toList, "")
 }