Issue #18910: test_textView - since all tests require 'gui', make root global.

Subclass TextViewer to add mock methods instead of monkey-patching it.

Lib/idlelib/idle_test/test_textview.py

-'''Test the functions and main class method of textView.py.'''
+'''Test the functions and main class method of textView.py.
+
+Since all methods and functions create (or destroy) a TextViewer, which
+is a widget containing multiple widgets, all tests must be gui tests.
+Using mock Text would not change this.  Other mocks are used to retrieve
+information about calls.
+
+The coverage is essentially 100%.
+'''
+from test.support import requires
+requires('gui')
 
 import unittest
 import os
-from test.support import requires
 from tkinter import Tk, Text, TclError
 from idlelib import textView as tv
 from idlelib.idle_test.mock_idle import Func
 from idlelib.idle_test.mock_tk import Mbox
 
-orig_mbox = tv.tkMessageBox
+def setUpModule():
+    global root
+    root = Tk()
 
-class TextViewTest(unittest.TestCase):
+def tearDownModule():
+    global root
+    root.destroy()
+    del root
 
-    @classmethod
-    def setUpClass(cls):
-        requires('gui')
-        cls.root = Tk()
-        cls.TV = TV = tv.TextViewer
-        TV.transient = Func()
-        TV.grab_set = Func()
-        TV.wait_window = Func()
 
-    @classmethod
-    def tearDownClass(cls):
-        cls.root.destroy()
-        TV = cls.TV
-        del cls.root, cls.TV
-        del TV.transient, TV.grab_set, TV.wait_window
+class TV(tv.TextViewer):  # used by TextViewTest
+    transient = Func()
+    grab_set = Func()
+    wait_window = Func()
+
+class TextViewTest(unittest.TestCase):
 
     def setUp(self):
-        TV = self.TV
         TV.transient.__init__()
         TV.grab_set.__init__()
         TV.wait_window.__init__()
 
-
     def test_init_modal(self):
-        TV = self.TV
-        view = TV(self.root, 'Title', 'test text')
+        view = TV(root, 'Title', 'test text')
         self.assertTrue(TV.transient.called)
         self.assertTrue(TV.grab_set.called)
         self.assertTrue(TV.wait_window.called)
         view.Ok()
 
     def test_init_nonmodal(self):
-        TV = self.TV
-        view = TV(self.root, 'Title', 'test text', modal=False)
+        view = TV(root, 'Title', 'test text', modal=False)
         self.assertFalse(TV.transient.called)
         self.assertFalse(TV.grab_set.called)
         self.assertFalse(TV.wait_window.called)
         view.Ok()
 
     def test_ok(self):
-        view = self.TV(self.root, 'Title', 'test text', modal=False)
+        view = TV(root, 'Title', 'test text', modal=False)
         view.destroy = Func()
         view.Ok()
         self.assertTrue(view.destroy.called)
@@ -64,33 +66,32 @@ class textviewTest(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        requires('gui')
-        cls.root = Tk()
+        cls.orig_mbox = tv.tkMessageBox
         tv.tkMessageBox = Mbox
 
     @classmethod
     def tearDownClass(cls):
-        cls.root.destroy()
-        del cls.root
-        tv.tkMessageBox = orig_mbox
+        tv.tkMessageBox = cls.orig_mbox
+        del cls.orig_mbox
 
     def test_view_text(self):
         # If modal True, tkinter will error with 'can't invoke "event" command'
-        view = tv.view_text(self.root, 'Title', 'test text', modal=False)
+        view = tv.view_text(root, 'Title', 'test text', modal=False)
         self.assertIsInstance(view, tv.TextViewer)
 
     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)
+        view = tv.view_file(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 and view_file will not return anything
         testfile = os.path.join(test_dir, '../notthere.py')
-        view = tv.view_file(self.root, 'Title', testfile, modal=False)
+        view = tv.view_file(root, 'Title', testfile, modal=False)
         self.assertIsNone(view)
 
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)