diff -r 13e154067de3 Lib/idlelib/RstripExtension.py
--- a/Lib/idlelib/RstripExtension.py	Wed Jul 03 23:07:37 2013 +0200
+++ b/Lib/idlelib/RstripExtension.py	Thu Jul 04 15:45:17 2013 -0400
@@ -27,3 +27,9 @@
             text.delete('%i.%i' % (cur, cut), '%i.0 lineend' % cur)
 
         undo.undo_block_stop()
+
+if __name__ == "__main__":
+    from test import support; support.use_resources = ['gui']
+    import unittest
+    unittest.main('idlelib.idle_test.test_rstripextension', verbosity=2, 
+                                                            exit=False)
diff -r 13e154067de3 Lib/idlelib/idle_test/mock_idle.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/idlelib/idle_test/mock_idle.py	Thu Jul 04 15:45:17 2013 -0400
@@ -0,0 +1,18 @@
+from idlelib.idle_test.mock_tk import Text
+
+class mockEditorWindow:
+    
+    def __init__(self):
+        self.text = Text()
+        self.undo = mockUndoDelegator()
+    
+    def get_selection_indices(self):
+    	first = self.text.index('sel.first')
+    	last = self.text.index('sel.last')
+    	return first, last
+
+class mockUndoDelegator:
+	def undo_block_start(*args):
+		pass
+	def undo_block_stop(*args):
+		pass
diff -r 13e154067de3 Lib/idlelib/idle_test/mock_tk.py
--- a/Lib/idlelib/idle_test/mock_tk.py	Wed Jul 03 23:07:37 2013 +0200
+++ b/Lib/idlelib/idle_test/mock_tk.py	Thu Jul 04 15:45:17 2013 -0400
@@ -61,3 +61,110 @@
     showerror = Mbox_func()    # None
     showinfo = Mbox_func()     # None
     showwarning = Mbox_func()  # None
+
+class Text:
+    def __init__(self):
+        self.data = ['']
+
+    def bind(*args):
+        pass
+
+    def setData(self, text):
+        # Used splitlines and retained newline because Tkinter docs
+        # say that referring to indexes "out of bounds" refer to the newline
+        # character at the end of a line or the last line. 
+        self.data = text.splitlines(True)
+
+    def getData(self):
+        return ''.join(self.data)
+
+    def _decode(self, position):  # private helper
+        """
+        Takes Text index (eg. '2.5') and returns index in self.data.
+        """
+        position = str(position)   # Tkinter allows floats to be passed in
+        if position == 'end':
+            return len(self.data) - 1, len(self.data[len(self.data)-1])
+        line, col = position.split('.')
+        line = int(line)
+        if line > len(self.data): # Out of bounds equals "line beyond the last"
+            self.data.append('\n')
+            line = len(self.data) - 1
+            self.data[line-1] += '\n'
+            return line, 0
+        lineLength = len(self.data[line-1])
+        if col == '0 lineend':
+            col = lineLength - 1
+        elif int(col) >= lineLength:
+            col = lineLength - 1
+        elif int(col) < lineLength:
+            col = int(col)
+        return line - 1, col
+
+    def get(self, start, end=None):
+        startline, startcol = self._decode(start)
+        if startline > len(self.data):
+            startline = len(self.data) - 1
+        if end is None:
+            return self.data[startline][startcol]
+        else:
+            endline, endcol = self._decode(end)
+            if startline == endline:
+                return self.data[startline][startcol:endcol]
+            else:
+                lines = [self.data[startline][startcol:]]
+                for i in range(startline+1, endline):
+                    lines.append(self.data[i])
+                lines.append(self.data[endline][:endcol])
+                return ''.join(lines)
+
+    def delete(self, start, end=None):
+        startline, startcol = self._decode(start)
+        if end is None:
+            self.data[startline] = self.data[startline][:startcol] + 
+                                   self.data[startline][startcol+1:]
+            return
+        else:
+            endline, endcol = self._decode(end)
+            if startline == endline:
+                self.data[startline] = self.data[startline][:startcol] + 
+                                       self.data[endline][endcol:]
+            else:
+                self.data[startline] = self.data[startline][:startcol] + 
+                                       self.data[endline][endcol:]
+                for i in range(startline+1, endline):
+                    del self.data[startline+1]
+        return
+
+    def index(self, position):
+        if position == 'end':
+            return str(len(self.data)) + '.' + str(len(self.data[-1]))
+        if position == 'sel.first':
+            return '1.0'
+        if position == 'sel.last':
+            return 'end'
+        # TODO: support other index types (eg. line.column, line.end, ...).
+
+    def insert(self, position, text):
+        text = text.splitlines(True)
+        line, col = self._decode(position)
+        splitline = [self.data[line][:col], self.data[line][col:]]
+        self.data[line] = splitline[0] + text[0]
+        for i in range(1, len(text)):
+            self.data.insert(line+i, text[i])
+        self.data[line+len(text)-1] += splitline[1]
+
+    def tag_remove(self, *args):
+        pass
+
+    def mark_set(self, *args):
+        pass
+
+    def undo_block_start(self, *args):
+        pass
+
+    def undo_block_stop(self, *args):
+        pass
+
+    def see(self, *args):
+        pass