Fixed issue with InvalidArgumentException when a string is passed as …

…chunk-size.

src/Fusonic/Linq/Linq.php

@@ -195,7 +195,7 @@ public function aggregate(callable $func, $seed = null)
     public function chunk($chunksize)
     {
         if ($chunksize < 1) {
-            throw new \InvalidArgumentException("chunksize", $chunksize);
+            throw new \InvalidArgumentException("'{$chunksize}' is not a valid chunk size.");
         }
 
         return Linq::from(new ChunkIterator($this->iterator, $chunksize));

tests/Fusonic/Linq/Test/ChunkTest.php

@@ -67,6 +67,14 @@ public function testChunk_throwsException_IfchunksizeIsInvalid()
         $this->assertException(function () {
             Linq::from([])->chunk(-1);
         }, self::ExceptionName_InvalidArgument);
+
+        $this->assertException(function () {
+            Linq::from([])->chunk(null);
+        }, self::ExceptionName_InvalidArgument);
+
+        $this->assertException(function () {
+            Linq::from([])->chunk("");
+        }, self::ExceptionName_InvalidArgument);
     }
 
     public function testChunk_ReturnsChunkedElementsAccordingToChunksize()