class_docstr: Test functions that display files.
  
  While somewhat redundant with gui-based test_file_dialog,
  these unit tests run on all buildbots, not just a few.
class_docstr_tok: ["Test","functions","that","display","files",".","While","somewhat","redundant","with","gui-based","test_file_dialog",",","these","unit","tests","run","on","all","buildbots",",","not","just","a","few","."]
code: def test_file_display(self):
      for handler in (
          self.dialog.idle_credits,
          self.dialog.idle_readme,
          self.dialog.idle_news,
      ):
          self.error.message = ""
          self.view.called = False
          with self.subTest(handler=handler):
              handler()
              self.assertEqual(self.error.message, "")
              self.assertEqual(self.view.called, True)
  
imports: from idlelib import help_about
  import unittest
  from test.support import requires, findfile
  from tkinter import Tk, TclError
  from idlelib.idle_test.mock_idle import Func
  from idlelib.idle_test.mock_tk import Mbox_func
  from idlelib import textview
  import os.path
  from platform import python_version
label_desc: Use image node_id 3 for calling the DisplayFileTest obj's underlying member method code with example usage: obj.test_file_display() without return types