Index: Lib/email/test/test_email.py =================================================================== --- Lib/email/test/test_email.py (revision 87407) +++ Lib/email/test/test_email.py (working copy) @@ -180,6 +180,17 @@ self.assertRaises(errors.HeaderParseError, msg.set_boundary, 'BOUNDARY') + def test_make_boundary(self): + msg = MIMEMultipart('form-data') + # Note that when the boundary gets created is an implementation + # detail and might change. + self.assertEqual(msg.items()[0][1], 'multipart/form-data') + # Trigger creation of boundary + msg.as_string() + self.assertEqual(msg.items()[0][1][:33], + 'multipart/form-data; boundary="==') + # XXX: there ought to be tests of the uniqueness of the boundary, too. + def test_message_rfc822_only(self): # Issue 7970: message/rfc822 not in multipart parsed by # HeaderParser caused an exception when flattened. Index: Lib/email/generator.py =================================================================== --- Lib/email/generator.py (revision 87407) +++ Lib/email/generator.py (working copy) @@ -226,7 +226,8 @@ # Create a boundary that doesn't appear in any of the # message texts. alltext = self._encoded_NL.join(msgtexts) - msg.set_boundary(self._make_boundary(alltext)) + boundary = self._make_boundary(alltext) + msg.set_boundary(boundary) # If there's a preamble, write it out, with a trailing CRLF if msg.preamble is not None: self.write(msg.preamble + self._NL)