diff -r 942a7061e8ad Lib/idlelib/RstripExtension.py
--- a/Lib/idlelib/RstripExtension.py	Fri Jun 21 19:08:06 2013 +0200
+++ b/Lib/idlelib/RstripExtension.py	Fri Jun 21 17:44:53 2013 -0400
@@ -27,3 +27,7 @@
             text.delete('%i.%i' % (cur, cut), '%i.0 lineend' % cur)
 
         undo.undo_block_stop()
+
+if __name__ == '__main__':
+    import unittest
+    unittest.main('idlelib.idle_test.test_rstripextension', verbosity=2, exit=False)
diff -r 942a7061e8ad Lib/idlelib/idle_test/mock_ewin.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/idlelib/idle_test/mock_ewin.py	Fri Jun 21 17:44:53 2013 -0400
@@ -0,0 +1,17 @@
+import tkinter
+from idlelib.UndoDelegator import UndoDelegator
+from tkinter.ttk import setup_master
+
+class Ewin:
+    def __init__(self, flist=None, filename=None, key=None, root=None):
+        self.flist = flist
+        self.filename = filename
+        self.key = key
+        self.root = setup_master()
+        self.text = tkinter.Text()
+        self.undo = UndoDelegator()
+
+    def _close(self):
+    	self.text = None
+    	self.undo = None
+    	self.root.destroy()
diff -r 942a7061e8ad Lib/idlelib/idle_test/test_rstripextension.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/idlelib/idle_test/test_rstripextension.py	Fri Jun 21 17:44:53 2013 -0400
@@ -0,0 +1,42 @@
+import unittest
+import idlelib.RstripExtension as rs
+import textwrap
+from idlelib.idle_test.mock_ewin import Ewin
+from test.support import requires
+
+requires('gui')
+class Test_rstripextension(unittest.TestCase):
+
+    def setUp(self):
+        self.mockEditorWindow = Ewin()
+        self.rstripextension = rs.RstripExtension(self.mockEditorWindow)
+
+    def tearDown(self):
+        self.rstripextension = None
+        self.mockEditorWindow._close()
+        
+    def test_do_rstrip(self):
+        # Note: Tkinter always adds a newline at the end of the text widget,
+        # hence the newline in the expected_text string
+
+        test_text = textwrap.dedent("""\
+            Here is         
+            some text                 
+            that has            
+            whitespace at the end       
+            of each line.            """)
+ 
+        expected_text = textwrap.dedent("""\
+            Here is
+            some text
+            that has
+            whitespace at the end
+            of each line.\n""")
+
+        self.mockEditorWindow.text.insert(1.0, test_text)
+        self.rstripextension.do_rstrip()
+        test_text = self.mockEditorWindow.text.get(1.0, "end")
+        self.assertEqual(test_text, expected_text)
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2, exit=False)