Fix MultiSet#toString and MultiDict#toString

src/main/scala/scala/collection/MultiDict.scala

@@ -13,6 +13,8 @@ trait MultiDict[K, V]
     with MultiDictOps[K, V, MultiDict, MultiDict[K, V]]
     with Equals {
 
+  override protected[this] def className: String = "MultiDict"
+
   def multiDictFactory: MapFactory[MultiDict] = MultiDict
   override protected def fromSpecific(coll: IterableOnce[(K, V)]): MultiDict[K, V] = multiDictFactory.from(coll)
   override protected def newSpecificBuilder: mutable.Builder[(K, V), MultiDict[K, V]] = multiDictFactory.newBuilder
@@ -196,6 +198,8 @@ trait MultiDictOps[K, V, +CC[X, Y] <: MultiDict[X, Y], +C <: MultiDict[K, V]]
   def filterSets(p: ((K, Set[V])) => Boolean): C =
     fromSpecificSets(new View.Filter(sets, p, isFlipped = false))
 
+  override def addString(sb: StringBuilder, start: String, sep: String, end: String): StringBuilder =
+    iterator.map { case (k, v) => s"$k -> $v" }.addString(sb, start, sep, end)
 }
 
 object MultiDictOps {

src/main/scala/scala/collection/MultiSet.scala

@@ -12,6 +12,8 @@ trait MultiSet[A]
     with MultiSetOps[A, MultiSet, MultiSet[A]]
     with Equals {
 
+  override protected[this] def className: String = "MultiSet"
+
   override def iterableFactory: IterableFactory[MultiSet] = MultiSet
   override protected def fromSpecific(coll: IterableOnce[A]): MultiSet[A] = iterableFactory.from(coll)
   override protected def newSpecificBuilder: mutable.Builder[A, MultiSet[A]] = iterableFactory.newBuilder

src/test/scala/scala/collection/MultiMapTest.scala → src/test/scala/scala/collection/MultiDictTest.scala

@@ -6,7 +6,7 @@ import scala.collection.immutable.List
 import org.junit.{Assert, Test}
 
 @RunWith(classOf[JUnit4])
-class MultiMapTest {
+class MultiDictTest {
 
   @Test
   def equality(): Unit = {
@@ -72,5 +72,51 @@ class MultiMapTest {
     val filteredT: MultiDict[String, Int] = filtered
     Assert.assertEquals(Seq.empty, filtered.toSeq)
   }
+  @Test
+  def testToString(): Unit = {
+
+    val prefix = "MultiDict("
+    val suffix = ")"
+
+    def run(ms: MultiDict[Int, Int]): Unit = {
+      val actual = ms.toString
+      assert(actual.startsWith(prefix), s"`$actual` does not start with `$prefix`")
+      assert(actual.endsWith(suffix), s"`$actual` does not end with `$suffix`")
+
+      // The order of elements in the multiset are not defined, so this test should be robust to order changes
+
+      val expected =
+        actual
+          .stripPrefix(prefix)
+          .stripSuffix(suffix)
+          .split(",")
+          .iterator
+          .flatMap { s =>
+            if (s.isEmpty) None
+            else {
+              val Array(keyString, valueString) = s.split("->")
+              Some(keyString.trim.toInt -> valueString.trim.toInt)
+            }
+          }
+          .to(MultiDict)
+      Assert.assertEquals(ms, expected)
+    }
+
+    def runForFactory(factory: MapFactory[MultiDict]): Unit = {
+      Assert.assertEquals(factory().toString, s"$prefix$suffix")
+      Assert.assertEquals(factory(1 -> 1).toString, s"${prefix}1 -> 1${suffix}")
+
+      run(factory())
+      run(factory(1 -> 1))
+      run(factory(1234 -> 2))
+      run(factory(1 -> 5,2 -> 6,3 -> 7))
+      run(factory(1 -> 1,1 -> 2,1 -> 3,2 -> 1,3 -> 3))
+      run(factory(1 -> 1,1 -> 2,1 -> 3,2 -> 4,2 -> 5,2 -> 6,2 -> 7,3 -> 8))
+    }
+
+    runForFactory(MultiDict)
+    runForFactory(mutable.MultiDict)
+    runForFactory(immutable.MultiDict)
+  }
 
 }

src/test/scala/scala/collection/MultiSetTest.scala

@@ -46,4 +46,43 @@ class MultiSetTest {
     )
   }
 
+  @Test
+  def testToString(): Unit = {
+
+    def run(ms: MultiSet[Int]): Unit = {
+      val actual = ms.toString
+      assert(actual.startsWith("MultiSet("), s"`$actual` does not start with `MultiSet(`")
+      assert(actual.endsWith(")"), s"`$actual` does not end with `)`")
+
+      // The order of elements in the multiset are not defined, so this test should be robust to order changes
+      Assert.assertEquals(ms,
+        actual
+          .stripPrefix("MultiSet(")
+          .stripSuffix(")")
+          .split(",")
+          .iterator
+          .flatMap (_.trim match {
+            case "" => None
+            case s => Some(s.toInt)
+          })
+          .to(MultiSet))
+    }
+
+    def runForFactory(factory: IterableFactory[MultiSet]): Unit = {
+      Assert.assertEquals(factory().toString, "MultiSet()")
+      Assert.assertEquals(factory(1).toString, "MultiSet(1)")
+
+      run(factory())
+      run(factory(1))
+      run(factory(1234))
+      run(factory(1,2,3))
+      run(factory(1,1,1,2,3))
+      run(factory(1,1,1,2,2,2,2,3))
+    }
+
+    runForFactory(MultiSet)
+    runForFactory(mutable.MultiSet)
+    runForFactory(immutable.MultiSet)
+  }
+
 }