code: def test_invaliddir(self):
      with captured_stdout() as s:
          filelist = list(grep.findfiles("invaliddir", "*.*", False))
      self.assertEqual(filelist, [])
      self.assertIn("invalid", s.getvalue())
  
imports: from idlelib import grep
  import unittest
  from test.support import captured_stdout
  from idlelib.idle_test.mock_tk import Var
  import os
  import re
label_desc: Use image node_id 3 for calling the FindfilesTest obj's underlying member method code with example usage: obj.test_invaliddir() without return types