commit df72f3e63c93be7dbc519bccab7daf1871d704a8
Author: Victor Stinner <victor.stinner@gmail.com>
Date:   Tue Aug 8 14:28:17 2017 +0200

    tooling

diff --git a/Lib/test/test_ttk_guionly.py b/Lib/test/test_ttk_guionly.py
index 462665d..a52314c 100644
--- a/Lib/test/test_ttk_guionly.py
+++ b/Lib/test/test_ttk_guionly.py
@@ -30,5 +30,9 @@ def test_main():
     support.run_unittest(
             *runtktests.get_tests(text=False, packages=['test_ttk']))
 
+    support.gc_collect()
+    if ttk.Widget.INSTANCE > 0:
+        raise Exception("leaking %s ttk widgets" % ttk.Widget.INSTANCE)
+
 if __name__ == '__main__':
     test_main()
diff --git a/Lib/tkinter/__init__.py b/Lib/tkinter/__init__.py
index deea791..88d8c9f 100644
--- a/Lib/tkinter/__init__.py
+++ b/Lib/tkinter/__init__.py
@@ -2300,6 +2300,9 @@ class BaseWidget(Misc):
         if self._name in self.master.children:
             del self.master.children[self._name]
         Misc.destroy(self)
+        if self.children:
+            raise Exception("destroy() doesn't clear all children: %s"
+                            % self.children)
     def _do(self, name, args=()):
         # XXX Obsolete -- better use self.tk.call directly!
         return self.tk.call((self._w, name) + args)
diff --git a/Lib/tkinter/test/support.py b/Lib/tkinter/test/support.py
index dd155fa..64ef992 100644
--- a/Lib/tkinter/test/support.py
+++ b/Lib/tkinter/test/support.py
@@ -22,6 +22,11 @@ class AbstractTkTest:
     @classmethod
     def tearDownClass(cls):
         cls.root.update_idletasks()
+
+        widgets = cls.root.grid_slaves()
+        for widget in widgets:
+            widget.destroy()
+
         cls.root.destroy()
         del cls.root
         tkinter._default_root = None
diff --git a/Lib/tkinter/ttk.py b/Lib/tkinter/ttk.py
index 3ecc004..1e23808 100644
--- a/Lib/tkinter/ttk.py
+++ b/Lib/tkinter/ttk.py
@@ -531,6 +531,7 @@ class Style(object):
 
 class Widget(tkinter.Widget):
     """Base class for Tk themed widgets."""
+    INSTANCE = 0
 
     def __init__(self, master, widgetname, kw=None):
         """Constructs a Ttk Widget with the parent master.
@@ -557,6 +558,11 @@ class Widget(tkinter.Widget):
             # Load tile now, if needed
             _load_tile(master)
         tkinter.Widget.__init__(self, master, widgetname, kw=kw)
+        Widget.INSTANCE += 1
+
+
+    def __del__(self):
+        Widget.INSTANCE -= 1
 
 
     def identify(self, x, y):