diff -r 347647a1f798 Lib/idlelib/RstripExtension.py
--- a/Lib/idlelib/RstripExtension.py	Mon Jun 24 18:12:57 2013 +0100
+++ b/Lib/idlelib/RstripExtension.py	Mon Jun 24 19:03:44 2013 -0400
@@ -27,3 +27,8 @@
             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 347647a1f798 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	Mon Jun 24 19:03:44 2013 -0400
@@ -0,0 +1,49 @@
+import unittest
+import textwrap
+import idlelib.RstripExtension as rs
+import idlelib.EditorWindow as ew
+from tkinter.ttk import setup_master
+from test.support import requires
+
+class Test_rstripextension(unittest.TestCase):
+    
+    @classmethod
+    def setUpClass(cls):
+        requires('gui')
+    
+    def setUp(self):
+        self.root = setup_master()
+        self.editwindow = ew.EditorWindow(root=self.root)
+        self.rstripextension = rs.RstripExtension(self.editwindow)
+        
+    def tearDown(self):
+        self.rstripextension = None
+        self.editwindow = None
+        self.root.destroy()
+        
+    def test_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.editwindow.text.insert(1.0, test_text)
+        self.rstripextension.do_rstrip()
+        test_text = self.editwindow.text.get(1.0, "end")
+        self.assertEqual(test_text, expected_text)
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2, exit=False)
+