diff --git a/tests/FunctionsTest.php b/tests/FunctionsTest.php
index 61c2ab9..37e5ade 100644
--- a/tests/FunctionsTest.php
+++ b/tests/FunctionsTest.php
@@ -13,6 +13,7 @@
 use ArrayIterator;
 use Closure;
 use Exception;
+use InvalidArgumentException;
 use function
     Noz\collect,
     Noz\invoke,
@@ -293,4 +294,20 @@ public function testNormalizeOffsetThrowsExceptionForInvalidOffset()
     {
         normalize_offset('chooochooo');
     }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testNormalizeOffsetWillThrowExceptionIfPassedNegativeOffsetWithoutCount()
+    {
+        normalize_offset(-10, null);
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testGetCountThrowsExceptionOnInvalidInput()
+    {
+        normalize_offset('chooochooo');
+    }
 }