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.

1 files changed, 146 insertions, 2 deletions

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)
+  }
 }