code: def test_view_file(self):
      test_dir = os.path.dirname(__file__)
      testfile = os.path.join(test_dir, "test_textview.py")
      view = tv.view_file(self.root, "Title", testfile, modal=False)
      self.assertIsInstance(view, tv.TextViewer)
      self.assertIn("Test", view.textView.get("1.0", "1.end"))
      view.Ok()
  
      # Mock messagebox will be used; view_file will return None.
      testfile = os.path.join(test_dir, "../notthere.py")
      view = tv.view_file(self.root, "Title", testfile, modal=False)
      self.assertIsNone(view)
  
imports: import unittest
  import os
  from test.test_support import requires
  from Tkinter import Tk
  from idlelib import textView
  from idlelib.idle_test.mock_idle import Func
  from idlelib.idle_test.mock_tk import Mbox
label_desc: Use image node_id 4 for calling the ViewFunctionTest obj's underlying member method code with example usage: obj.test_view_file() without return types