Issue 20567: Revise idle_test/README.txt and some tests to match new advice.

Lib/idlelib/idle_test/README.txt

@@ -56,40 +56,44 @@ requires('gui')
 
 To guard a test class, put "requires('gui')" in its setUpClass function.
 
-To avoid interfering with other GUI tests, all GUI objects must be
-destroyed and deleted by the end of the test.  Widgets, such as a Tk
-root, created in a setUpX function, should be destroyed in the
-corresponding tearDownX.  Module and class widget attributes should also
-be deleted.
+To avoid interfering with other gui tests, all gui objects must be destroyed and
+deleted by the end of the test.  The Tk root created in a setUpX function should
+be destroyed in the corresponding tearDownX and the module or class attribute
+deleted.  Others widgets should descend from the single root and the attributes
+deleted BEFORE root is destroyed.  See https://bugs.python.org/issue20567.
 
     @classmethod
     def setUpClass(cls):
         requires('gui')
         cls.root = tk.Tk()
+        cls.text = tk.Text(root)
 
     @classmethod
     def tearDownClass(cls):
+        del cls.text
         cls.root.destroy()
         del cls.root
 
 
 Requires('gui') causes the test(s) it guards to be skipped if any of
-a few conditions are met:
-    
+these conditions are met:
+
  - The tests are being run by regrtest.py, and it was started without
    enabling the "gui" resource with the "-u" command line option.
-   
+
  - The tests are being run on Windows by a service that is not allowed
    to interact with the graphical environment.
-   
+
+ - The tests are being run on Linux and X Windows is not available.
+
  - The tests are being run on Mac OSX in a process that cannot make a
    window manager connection.
-   
+
  - tkinter.Tk cannot be successfully instantiated for some reason.
- 
+
  - test.support.use_resources has been set by something other than
    regrtest.py and does not contain "gui".
-   
+
 Tests of non-GUI operations should avoid creating tk widgets. Incidental
 uses of tk variables and messageboxes can be replaced by the mock
 classes in idle_test/mock_tk.py. The mock text handles some uses of the

Lib/idlelib/idle_test/test_autocomplete.py

@@ -33,9 +33,8 @@ class AutoCompleteTest(unittest.TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.editor, cls.text
         cls.root.destroy()
-        del cls.text
-        del cls.editor
         del cls.root
 
     def setUp(self):

Lib/idlelib/idle_test/test_autoexpand.py

@@ -25,10 +25,10 @@ class AutoExpandTest(unittest.TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.text, cls.auto_expand
         if hasattr(cls, 'tk'):
             cls.tk.destroy()
             del cls.tk
-        del cls.text, cls.auto_expand
 
     def tearDown(self):
         self.text.delete('1.0', 'end')

Lib/idlelib/idle_test/test_formatparagraph.py

@@ -276,10 +276,9 @@ class FormatEventTest(unittest.TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.text, cls.formatter
         cls.root.destroy()
         del cls.root
-        del cls.text
-        del cls.formatter
 
     def test_short_line(self):
         self.text.insert('1.0', "Short line\n")

Lib/idlelib/idle_test/test_percolator.py

@@ -40,9 +40,9 @@ class PercolatorTest(unittest.TestCase):
 
     @classmethod
     def tearDownClass(cls):
-        cls.text.destroy()
+        del cls.text
         cls.root.destroy()
-        del cls.text, cls.root
+        del cls.root
 
     def setUp(self):
         self.percolator = Percolator(self.text)

Lib/idlelib/idle_test/test_replacedialog.py

@@ -31,8 +31,9 @@ class ReplaceDialogTest(unittest.TestCase):
     @classmethod
     def tearDownClass(cls):
         se.tkMessageBox = orig_mbox
+        del cls.text, cls.dialog, cls.engine
         cls.root.destroy()
-        del cls.text, cls.dialog, cls.engine, cls.root
+        del cls.root
 
     def setUp(self):
         self.text.insert('insert', 'This is a sample sTring')

Lib/idlelib/idle_test/test_textview.py

@@ -22,7 +22,8 @@ def setUpModule():
     root = Tk()
 
 def tearDownModule():
-    global root
+    global root, TV
+    del TV
     root.destroy()  # pyflakes falsely sees root as undefined
     del root
 

Lib/idlelib/idle_test/test_undodelegator.py

@@ -23,8 +23,9 @@ class UndoDelegatorTest(unittest.TestCase):
     @classmethod
     def tearDownClass(cls):
         cls.percolator.redir.close()
+        del cls.percolator, cls.text
         cls.root.destroy()
-        del cls.percolator, cls.text, cls.root
+        del cls.root
 
     def setUp(self):
         self.delegator = UndoDelegator()

Lib/idlelib/idle_test/test_widgetredir.py

@@ -14,14 +14,14 @@ class InitCloseTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         requires('gui')
-        cls.tk = Tk()
-        cls.text = Text(cls.tk)
+        cls.root = Tk()
+        cls.text = Text(cls.root)
 
     @classmethod
     def tearDownClass(cls):
-        cls.text.destroy()
-        cls.tk.destroy()
-        del cls.text, cls.tk
+        del cls.text
+        cls.root.destroy()
+        del cls.root
 
     def test_init(self):
         redir = WidgetRedirector(self.text)
@@ -43,14 +43,14 @@ class WidgetRedirectorTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         requires('gui')
-        cls.tk = Tk()
-        cls.text = Text(cls.tk)
+        cls.root = Tk()
+        cls.text = Text(cls.root)
 
     @classmethod
     def tearDownClass(cls):
-        cls.text.destroy()
-        cls.tk.destroy()
-        del cls.text, cls.tk
+        del cls.text
+        cls.root.destroy()
+        del cls.root
 
     def setUp(self):
         self.redir = WidgetRedirector(self.text)
@@ -108,13 +108,13 @@ class WidgetRedirectorTest(unittest.TestCase):
     def test_command_dispatch(self):
         # Test that .__init__ causes redirection of tk calls
         # through redir.dispatch
-        self.tk.call(self.text._w, 'insert', 'hello')
+        self.root.call(self.text._w, 'insert', 'hello')
         self.assertEqual(self.func.args, ('hello',))
         self.assertEqual(self.text.get('1.0', 'end'), '\n')
         # Ensure that called through redir .dispatch and not through
         # self.text.insert by having mock raise TclError.
         self.func.__init__(TclError())
-        self.assertEqual(self.tk.call(self.text._w, 'insert', 'boo'), '')
+        self.assertEqual(self.root.call(self.text._w, 'insert', 'boo'), '')