diff -r a37440dec1b6 Lib/idlelib/FormatParagraph.py
--- a/Lib/idlelib/FormatParagraph.py	Tue Apr 15 23:44:14 2014 -0400
+++ b/Lib/idlelib/FormatParagraph.py	Wed Apr 16 00:34:41 2014 -0400
@@ -32,7 +32,7 @@
     def close(self):
         self.editwin = None
 
-    def format_paragraph_event(self, event):
+    def format_paragraph_event(self, event, limit=None):
         """Formats paragraph to a max width specified in idleConf.
 
         If text is selected, format_paragraph_event will start breaking lines
@@ -41,9 +41,12 @@
         If no text is selected, format_paragraph_event uses the current
         cursor location to determine the paragraph (lines of text surrounded
         by blank lines) and formats it.
+        
+        The length limit parameter is for testing with a known value.
         """
-        maxformatwidth = idleConf.GetOption(
-                'main', 'FormatParagraph', 'paragraph', type='int')
+        if limit == None:
+            limit = idleConf.GetOption(
+                    'main', 'FormatParagraph', 'paragraph', type='int')
         text = self.editwin.text
         first, last = self.editwin.get_selection_indices()
         if first and last:
@@ -53,9 +56,9 @@
             first, last, comment_header, data = \
                     find_paragraph(text, text.index("insert"))
         if comment_header:
-            newdata = reformat_comment(data, maxformatwidth, comment_header)
+            newdata = reformat_comment(data, limit, comment_header)
         else:
-            newdata = reformat_paragraph(data, maxformatwidth)
+            newdata = reformat_paragraph(data, limit)
         text.tag_remove("sel", "1.0", "end")
 
         if newdata != data: