diff -r 30b6cd2b3440 Lib/idlelib/dynoption.py
--- a/Lib/idlelib/dynoption.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/dynoption.py	Mon Jun 20 17:25:59 2016 +0300
@@ -36,7 +36,7 @@ class DynOptionMenu(OptionMenu):
 def _dyn_option_menu(parent):  # htest #
     from tkinter import Toplevel
 
-    top = Toplevel()
+    top = Toplevel(parent)
     top.title("Tets dynamic option menu")
     top.geometry("200x100+%d+%d" % (parent.winfo_rootx() + 200,
                   parent.winfo_rooty() + 150))
diff -r 30b6cd2b3440 Lib/idlelib/idle_test/htest.py
--- a/Lib/idlelib/idle_test/htest.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/idle_test/htest.py	Mon Jun 20 17:25:59 2016 +0300
@@ -364,7 +364,7 @@ def run(*tests):
                 test = getattr(mod, test_name)
                 test_list.append((test_spec, test))
 
-    test_name = tk.StringVar('')
+    test_name = tk.StringVar(root)
     callable_object = None
     test_kwds = None
 
diff -r 30b6cd2b3440 Lib/idlelib/idle_test/test_searchbase.py
--- a/Lib/idlelib/idle_test/test_searchbase.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/idle_test/test_searchbase.py	Mon Jun 20 17:25:59 2016 +0300
@@ -74,7 +74,7 @@ class SearchDialogBaseTest(unittest.Test
     def test_make_entry(self):
         equal = self.assertEqual
         self.dialog.row = 0
-        self.dialog.top = Toplevel(self.root)
+        self.dialog.top = self.root
         entry, label = self.dialog.make_entry("Test:", 'hello')
         equal(label['text'], 'Test:')
 
@@ -87,6 +87,7 @@ class SearchDialogBaseTest(unittest.Test
         equal(self.dialog.row, 1)
 
     def test_create_entries(self):
+        self.dialog.top = self.root
         self.dialog.row = 0
         self.engine.setpat('hello')
         self.dialog.create_entries()
@@ -94,7 +95,7 @@ class SearchDialogBaseTest(unittest.Test
 
     def test_make_frame(self):
         self.dialog.row = 0
-        self.dialog.top = Toplevel(self.root)
+        self.dialog.top = self.root
         frame, label = self.dialog.make_frame()
         self.assertEqual(label, '')
         self.assertIsInstance(frame, Frame)
@@ -104,7 +105,7 @@ class SearchDialogBaseTest(unittest.Test
         self.assertIsInstance(frame, Frame)
 
     def btn_test_setup(self, meth):
-        self.dialog.top = Toplevel(self.root)
+        self.dialog.top = self.root
         self.dialog.row = 0
         return meth()
 
@@ -145,12 +146,13 @@ class SearchDialogBaseTest(unittest.Test
                     self.assertEqual(var.get(), state)
 
     def test_make_button(self):
-        self.dialog.top = Toplevel(self.root)
+        self.dialog.top = self.root
         self.dialog.buttonframe = Frame(self.dialog.top)
         btn = self.dialog.make_button('Test', self.dialog.close)
         self.assertEqual(btn['text'], 'Test')
 
     def test_create_command_buttons(self):
+        self.dialog.top = self.root
         self.dialog.create_command_buttons()
         # Look for close button command in buttonframe
         closebuttoncommand = ''
diff -r 30b6cd2b3440 Lib/idlelib/idle_test/test_text.py
--- a/Lib/idlelib/idle_test/test_text.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/idle_test/test_text.py	Mon Jun 20 17:25:59 2016 +0300
@@ -1,17 +1,19 @@
-# Test mock_tk.Text class against tkinter.Text class by running same tests with both.
+''' Test mock_tk.Text class against tkinter.Text class
+
+Run same tests with both by creating a mixin class.
+'''
 import unittest
 from test.support import requires
-
 from _tkinter import TclError
 
 class TextTest(object):
+    "Define items common to both sets of tests."
 
-    hw = 'hello\nworld'  # usual initial insert after initialization
+    hw = 'hello\nworld'  # Several tests insert this after after initialization.
     hwn = hw+'\n'  # \n present at initialization, before insert
 
-    Text = None
-    def setUp(self):
-        self.text = self.Text()
+    # setUpClass defines cls.Text and maybe cls.root.
+    # setUp defines self.text from Text and maybe root.
 
     def test_init(self):
         self.assertEqual(self.text.get('1.0'), '\n')
@@ -196,6 +198,10 @@ class MockTextTest(TextTest, unittest.Te
         from idlelib.idle_test.mock_tk import Text
         cls.Text = Text
 
+    def setUp(self):
+        self.text = self.Text()
+
+
     def test_decode(self):
         # test endflags (-1, 0) not tested by test_index (which uses +1)
         decode = self.text._decode
@@ -222,6 +228,9 @@ class TkTextTest(TextTest, unittest.Test
         cls.root.destroy()
         del cls.root
 
+    def setUp(self):
+        self.text = self.Text(self.root)
+
 
 if __name__ == '__main__':
     unittest.main(verbosity=2, exit=False)
diff -r 30b6cd2b3440 Lib/idlelib/percolator.py
--- a/Lib/idlelib/percolator.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/percolator.py	Mon Jun 20 17:25:59 2016 +0300
@@ -89,10 +89,10 @@ def _percolator(parent):  # htest #
         (pin if var2.get() else pout)(t2)
 
     text.pack()
-    var1 = tk.IntVar()
+    var1 = tk.IntVar(parent)
     cb1 = tk.Checkbutton(box, text="Tracer1", command=toggle1, variable=var1)
     cb1.pack()
-    var2 = tk.IntVar()
+    var2 = tk.IntVar(parent)
     cb2 = tk.Checkbutton(box, text="Tracer2", command=toggle2, variable=var2)
     cb2.pack()
 
diff -r 30b6cd2b3440 Lib/idlelib/pyshell.py
--- a/Lib/idlelib/pyshell.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/pyshell.py	Mon Jun 20 17:25:59 2016 +0300
@@ -2,6 +2,7 @@
 
 try:
     from tkinter import *
+    # NoDefaultRoot()  # More testing is needed for permanent uncomment.
 except ImportError:
     print("** IDLE can't import Tkinter.\n"
           "Your Python may not be configured for Tk. **", file=sys.__stderr__)
@@ -1560,7 +1561,8 @@ def main():
         ext = '.png' if TkVersion >= 8.6 else '.gif'
         iconfiles = [os.path.join(icondir, 'idle_%d%s' % (size, ext))
                      for size in (16, 32, 48)]
-        icons = [PhotoImage(file=iconfile) for iconfile in iconfiles]
+        icons = [PhotoImage(master=root, file=iconfile)
+                 for iconfile in iconfiles]
         root.wm_iconphoto(True, *icons)
 
     fixwordbreaks(root)
diff -r 30b6cd2b3440 Lib/idlelib/undo.py
--- a/Lib/idlelib/undo.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/idlelib/undo.py	Mon Jun 20 17:25:59 2016 +0300
@@ -341,7 +341,7 @@ def _undo_delegator(parent):  # htest #
     import re
     import tkinter as tk
     from idlelib.percolator import Percolator
-    undowin = tk.Toplevel()
+    undowin = tk.Toplevel(parent)
     undowin.title("Test UndoDelegator")
     width, height, x, y = list(map(int, re.split('[x+]', parent.geometry())))
     undowin.geometry("+%d+%d"%(x, y + 150))
diff -r 30b6cd2b3440 Lib/test/test_idle.py
--- a/Lib/test/test_idle.py	Mon Jun 20 14:13:12 2016 +0200
+++ b/Lib/test/test_idle.py	Mon Jun 20 17:25:59 2016 +0300
@@ -6,6 +6,7 @@ import_module('threading')  # imported b
 tk = import_module('tkinter')  # imports _tkinter
 if tk.TkVersion < 8.5:
     raise unittest.SkipTest("IDLE requires tk 8.5 or later.")
+tk.NoDefaultRoot()
 idletest = import_module('idlelib.idle_test')
 
 # Without test_main present, regrtest.runtest_inner (line1219) calls