diff --git a/stegano/tools.py b/stegano/tools.py
index 0a88b66..f36057e 100755
--- a/stegano/tools.py
+++ b/stegano/tools.py
@@ -26,6 +26,7 @@ __revision__ = "$Date: 2016/08/03 $"
 __license__ = "GPLv3"
 
 import base64
+import itertools
 from functools import reduce
 
 def a2bits(chars):
@@ -80,7 +81,7 @@ def n_at_a_time(items, n, fillvalue):
     [(1, 2), (3, 4), (5, 'X')]
     """
     it = iter(items)
-    return its.izip_longest(*[it] * n, fillvalue=fillvalue)
+    return itertools.zip_longest(*[it] * n, fillvalue=fillvalue)
 
 def binary2base64(binary_file):
     """
diff --git a/tests/test_exifHeader.py b/tests/test_exifHeader.py
index b0ae24c..f26083b 100644
--- a/tests/test_exifHeader.py
+++ b/tests/test_exifHeader.py
@@ -34,8 +34,7 @@ from stegano import exifHeader
 class TestEXIFHeader(unittest.TestCase):
 
     def test_hide_empty_message(self):
-        """
-        Test hiding the empty string.
+        """Test hiding the empty string.
         """
         secret = exifHeader.hide("./tests/sample-files/20160505T130442.jpg",
                                 "./image.jpg", secret_message="")
diff --git a/tests/test_tools.py b/tests/test_tools.py
new file mode 100644
index 0000000..f667e17
--- /dev/null
+++ b/tests/test_tools.py
@@ -0,0 +1,57 @@
+#!/usr/bin/env python
+#-*- coding: utf-8 -*-
+
+# Stéganô - Stéganô is a basic Python Steganography module.
+# Copyright (C) 2010-2017  Cédric Bonhomme - https://www.cedricbonhomme.org
+#
+# For more information : https://github.com/cedricbonhomme/Stegano
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+__author__ = "Cedric Bonhomme"
+__version__ = "$Revision: 0.1 $"
+__date__ = "$Date: 2017/02/22 $"
+__revision__ = "$Date: 2017/02/22 $"
+__license__ = "GPLv3"
+
+import os
+import unittest
+import io
+
+from stegano import tools
+
+class TestEXIFHeader(unittest.TestCase):
+
+    def test_a2bits(self):
+        bits = tools.a2bits("Hello World!")
+        self.assertEqual(bits, '010010000110010101101100011011000110111100100000010101110110111101110010011011000110010000100001')
+
+    def test_a2bits_list(self):
+        list_of_bits = tools.a2bits_list("Hello World!")
+        self.assertEqual(list_of_bits, ['01001000',
+                                        '01100101',
+                                        '01101100',
+                                        '01101100',
+                                        '01101111',
+                                        '00100000',
+                                        '01010111',
+                                        '01101111',
+                                        '01110010',
+                                        '01101100',
+                                        '01100100',
+                                        '00100001'])
+
+    def test_n_at_a_time(self):
+        result = tools.n_at_a_time([1, 2, 3, 4, 5], 2, 'X')
+        self.assertEqual(list(result), [(1, 2), (3, 4), (5, 'X')])