diff -r ce89c5c3c786 Lib/test/test___all__.py
--- a/Lib/test/test___all__.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test___all__.py	Fri Dec 20 10:26:22 2013 -0600
@@ -112,6 +112,14 @@
                   ignored)
             print('Following modules failed to be imported:', failed_imports)
 
+def tearDownModule():
+    # suppress warning about os.environ changing due to tkinter being imported
+    try:
+        from tkinter import _fix
+        _fix.unfix_environ()
+    except Exception as e:
+        if support.verbose:
+            print('unfixing environ for tkinter failed: %s' % e)
 
 if __name__ == "__main__":
     unittest.main()
diff -r ce89c5c3c786 Lib/test/test_idle.py
--- a/Lib/test/test_idle.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test_idle.py	Fri Dec 20 10:26:22 2013 -0600
@@ -23,6 +23,14 @@
 # load_tests() if it finds it. (Unittest.main does the same.)
 load_tests = idletest.load_tests
 
+def setUpModule():
+    # make sure init.tcl can be found
+    tk._fix.fix_environ()
+
+def tearDownModule():
+    # suppress warning about os.environ changing
+    tk._fix.unfix_environ()
+
 if __name__ == '__main__':
     # Until unittest supports resources, we emulate regrtest's -ugui
     # so loaded tests run the same as if textually present here.
diff -r ce89c5c3c786 Lib/test/test_tcl.py
--- a/Lib/test/test_tcl.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test_tcl.py	Fri Dec 20 10:26:22 2013 -0600
@@ -9,8 +9,7 @@
 # Skip this test if the _tkinter module wasn't built.
 _tkinter = support.import_module('_tkinter')
 
-# Make sure tkinter._fix runs to set up the environment
-support.import_fresh_module('tkinter')
+from tkinter import _fix
 
 from tkinter import Tcl
 from _tkinter import TclError
@@ -269,13 +268,14 @@
 
 
 def setUpModule():
+    _fix.fix_environ()
     if support.verbose:
         tcl = Tcl()
         print('patchlevel =', tcl.call('info', 'patchlevel'))
 
+def tearDownModule():
+    _fix.unfix_environ()
 
-def test_main():
-    support.run_unittest(TclTest, TkinterTest, BigmemTclTest)
 
 if __name__ == "__main__":
-    test_main()
+    unittest.main()
diff -r ce89c5c3c786 Lib/test/test_tk.py
--- a/Lib/test/test_tk.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test_tk.py	Fri Dec 20 10:26:22 2013 -0600
@@ -2,8 +2,7 @@
 # Skip test if _tkinter wasn't built.
 support.import_module('_tkinter')
 
-# Make sure tkinter._fix runs to set up the environment
-support.import_fresh_module('tkinter')
+from tkinter import _fix
 
 # Skip test if tk cannot be initialized.
 from tkinter.test.support import check_tk_availability
@@ -18,8 +17,13 @@
         elif 'gui' not in support.use_resources:
             support.use_resources.append('gui')
 
+    # make sure init.tcl can be found
+    _fix.fix_environ()
     support.run_unittest(
             *runtktests.get_tests(text=False, packages=['test_tkinter']))
 
+    # suppress warning about os.environ changing
+    _fix.unfix_environ()
+
 if __name__ == '__main__':
     test_main(enable_gui=True)
diff -r ce89c5c3c786 Lib/test/test_ttk_guionly.py
--- a/Lib/test/test_ttk_guionly.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test_ttk_guionly.py	Fri Dec 20 10:26:22 2013 -0600
@@ -5,8 +5,7 @@
 # Skip this test if _tkinter wasn't built.
 support.import_module('_tkinter')
 
-# Make sure tkinter._fix runs to set up the environment
-support.import_fresh_module('tkinter')
+from tkinter import _fix
 
 # Skip test if tk cannot be initialized.
 from tkinter.test.support import check_tk_availability
@@ -30,11 +29,17 @@
         elif 'gui' not in support.use_resources:
             support.use_resources.append('gui')
 
+    # make sure init.tcl can be found
+    _fix.fix_environ()
     try:
         support.run_unittest(
                 *runtktests.get_tests(text=False, packages=['test_ttk']))
     finally:
+        # don't leave a window hanging around
         get_tk_root().destroy()
 
+    # suppress warning about os.environ changing
+    _fix.unfix_environ()
+
 if __name__ == '__main__':
     test_main(enable_gui=True)
diff -r ce89c5c3c786 Lib/test/test_ttk_textonly.py
--- a/Lib/test/test_ttk_textonly.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/test/test_ttk_textonly.py	Fri Dec 20 10:26:22 2013 -0600
@@ -4,14 +4,17 @@
 # Skip this test if _tkinter does not exist.
 support.import_module('_tkinter')
 
-# Make sure tkinter._fix runs to set up the environment
-support.import_fresh_module('tkinter')
-
+from tkinter import _fix
 from tkinter.test import runtktests
 
 def test_main():
+    # make sure init.tcl can be found
+    _fix.fix_environ()
     support.run_unittest(
             *runtktests.get_tests(gui=False, packages=['test_ttk']))
 
+    # suppress warning about os.environ changing
+    _fix.unfix_environ()
+
 if __name__ == '__main__':
     test_main()
diff -r ce89c5c3c786 Lib/tkinter/_fix.py
--- a/Lib/tkinter/_fix.py	Wed Dec 18 11:27:21 2013 -0800
+++ b/Lib/tkinter/_fix.py	Fri Dec 20 10:26:22 2013 -0600
@@ -46,33 +46,48 @@
             s = "\\" + s[3:]
         return s
 
-prefix = os.path.join(sys.base_prefix,"tcl")
-if not os.path.exists(prefix):
-    # devdir/../tcltk/lib
-    prefix = os.path.join(sys.base_prefix, os.path.pardir, "tcltk", "lib")
-    prefix = os.path.abspath(prefix)
-# if this does not exist, no further search is needed
-if os.path.exists(prefix):
-    prefix = convert_path(prefix)
-    if "TCL_LIBRARY" not in os.environ:
-        for name in os.listdir(prefix):
-            if name.startswith("tcl"):
-                tcldir = os.path.join(prefix,name)
-                if os.path.isdir(tcldir):
-                    os.environ["TCL_LIBRARY"] = tcldir
-    # Compute TK_LIBRARY, knowing that it has the same version
-    # as Tcl
-    import _tkinter
-    ver = str(_tkinter.TCL_VERSION)
-    if "TK_LIBRARY" not in os.environ:
-        v = os.path.join(prefix, 'tk'+ver)
-        if os.path.exists(os.path.join(v, "tclIndex")):
-            os.environ['TK_LIBRARY'] = v
-    # We don't know the Tix version, so we must search the entire
-    # directory
-    if "TIX_LIBRARY" not in os.environ:
-        for name in os.listdir(prefix):
-            if name.startswith("tix"):
-                tixdir = os.path.join(prefix,name)
-                if os.path.isdir(tixdir):
-                    os.environ["TIX_LIBRARY"] = tixdir
+orig_environ = os.environ.copy()
+
+def fix_environ():
+    # Add (TCL|TK|TIX)_LIBRARY vars to os.environ so init.tcl can be found
+    prefix = os.path.join(sys.base_prefix,"tcl")
+    if not os.path.exists(prefix):
+        # devdir/../tcltk/lib
+        prefix = os.path.join(sys.base_prefix, os.path.pardir, "tcltk", "lib")
+        prefix = os.path.abspath(prefix)
+    # if this does not exist, no further search is needed
+    if os.path.exists(prefix):
+        prefix = convert_path(prefix)
+        if "TCL_LIBRARY" not in os.environ:
+            for name in os.listdir(prefix):
+                if name.startswith("tcl"):
+                    tcldir = os.path.join(prefix,name)
+                    if os.path.isdir(tcldir):
+                        os.environ["TCL_LIBRARY"] = tcldir
+        # Compute TK_LIBRARY, knowing that it has the same version
+        # as Tcl
+        import _tkinter
+        ver = str(_tkinter.TCL_VERSION)
+        if "TK_LIBRARY" not in os.environ:
+            v = os.path.join(prefix, 'tk'+ver)
+            if os.path.exists(os.path.join(v, "tclIndex")):
+                os.environ['TK_LIBRARY'] = v
+        # We don't know the Tix version, so we must search the entire
+        # directory
+        if "TIX_LIBRARY" not in os.environ:
+            for name in os.listdir(prefix):
+                if name.startswith("tix"):
+                    tixdir = os.path.join(prefix,name)
+                    if os.path.isdir(tixdir):
+                        os.environ["TIX_LIBRARY"] = tixdir
+
+def unfix_environ(orig_environ=orig_environ):
+    # Use this function to undo the changes made by fix_environ()
+    for var in ['TCL_LIBRARY', 'TK_LIBRARY', 'TIX_LIBRARY']:
+        if var not in orig_environ:
+            os.environ.pop(var, None)
+
+del orig_environ
+
+# call unconditionally to match old behavior on import
+fix_environ()