diff -r bc3a34e47923 Lib/idlelib/IdleHistory.py
--- a/Lib/idlelib/IdleHistory.py	Sat Jul 13 04:05:42 2013 -0400
+++ b/Lib/idlelib/IdleHistory.py	Thu Jul 18 15:46:29 2013 +0530
@@ -1,14 +1,16 @@
 from idlelib.configHandler import idleConf
 
+
 class History:
 
-    def __init__(self, text, output_sep = "\n"):
+    def __init__(self, text, output_sep="\n"):
         self.text = text
         self.history = []
         self.history_prefix = None
         self.history_pointer = None
         self.output_sep = output_sep
-        self.cyclic = idleConf.GetOption("main", "History", "cyclic", 1, "bool")
+        self.cyclic = idleConf.GetOption("main", "History", "cyclic",
+                                         1, "bool")
         text.bind("<<history-previous>>", self.history_prev)
         text.bind("<<history-next>>", self.history_next)
 
@@ -86,3 +88,10 @@
             self.history.append(source)
         self.history_pointer = None
         self.history_prefix = None
+
+if __name__ == "__main__":
+    from test import support
+    support.use_resources = ['gui']
+    import unittest
+    unittest.main('idlelib.idle_test.test_idlehistory', verbosity=2,
+                  exit=False)
diff -r bc3a34e47923 Lib/idlelib/idle_test/test_idlehistory.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/idlelib/idle_test/test_idlehistory.py	Thu Jul 18 15:46:29 2013 +0530
@@ -0,0 +1,86 @@
+import unittest
+from test.support import requires
+
+from _tkinter import TclError
+import tkinter as tk
+
+import idlelib.IdleHistory as ihis
+from idlelib.idle_test.mock_tk import Text
+from idlelib.configHandler import idleConf
+
+
+class IdleHistoryMockTest(unittest.TestCase):
+    '''IdleHistory tests which can be done using mock_tk
+    '''
+
+    def setUp(self):
+        self.mytext = Text()
+        self.mytext.insert('1.0', "  idlehistory test  ")
+        self.myhistory = ihis.History(self.mytext)
+
+    def TearDown(self):
+        self.mytext = None
+        self.myhistory = None
+
+    def test_myhistory(self):
+        self.assertIs(self.myhistory.text, self.mytext)
+        self.assertEqual(self.myhistory.history, [])
+        self.assertIsNone(self.myhistory.history_prefix)
+        self.assertIsNone(self.myhistory.history_pointer)
+        self.assertEqual(self.myhistory.cyclic, idleConf.GetOption("main",
+                                                                   "History",
+                                                                   "cyclic", 1,
+                                                                   "bool"))
+        self.assertEqual(self.myhistory.output_sep, "\n")
+
+    def test_duplicates_history_store(self):
+        # source having length less than 3 (after stripped) should be avoided
+        source = self.mytext.get('1.0', '1.4')
+        self.myhistory.history_store(source)
+        self.assertEqual(self.myhistory.history, [])
+
+    def test_history_store(self):
+        source = self.mytext.get('1.0', '1.6')
+        self.myhistory.history_store(source)
+        self.assertEqual(self.myhistory.history, ['idle'])
+
+
+class IdleHistoryTKTest(unittest.TestCase):
+    '''IdleHistory tests which needs TK
+    '''
+    @classmethod
+    def setUpClass(cls):
+        requires('gui')
+        from tkinter import Tk, Text
+        cls.text = Text()
+        cls.text.insert('1.0', "  idlehistory test")
+        cls.text.mark_set("iomark", "1.6")
+        cls.mytkhistory = ihis.History(cls.text)
+        try:
+            cls.root = Tk()
+        except TclError as msg:
+            raise unittest.SkipTest('TclError: %s' % msg)
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.root.destroy()
+
+    def test_history_do_next(self):
+        '''
+        Test history_do function for history_next call
+        deletes text from 'iomark' and inserts history_prefix
+        '''
+        source = self.text.get("iomark", "end-1c")
+        self.mytkhistory.history_store(source)
+        self.text.mark_set("insert", "end-1c")
+        self.mytkhistory.history_prefix = "Done_history_test"
+        self.mytkhistory.history_pointer = 0
+        self.mytkhistory.history_do(0)
+        self.assertEqual(self.mytkhistory.text.get('1.0', '1.24'),
+                         "  idleDone_history_test")
+        self.assertIsNone(self.mytkhistory.history_pointer)
+        self.assertIsNone(self.mytkhistory.history_prefix)
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2, exit=2)