1 files changed, 39 insertions, 10 deletions
diff --git a/SCons/Tool/MSCommon/MSVC/ConfigTests.py b/SCons/Tool/MSCommon/MSVC/ConfigTests.py
index 570861c7d..052893093 100644
--- a/SCons/Tool/MSCommon/MSVC/ConfigTests.py
+++ b/SCons/Tool/MSCommon/MSVC/ConfigTests.py
@@ -31,28 +31,57 @@ from SCons.Tool.MSCommon import vc
 from SCons.Tool.MSCommon.MSVC import Config
 from SCons.Tool.MSCommon.MSVC.Exceptions import MSVCInternalError
 
-_VCVER = vc._VCVER
-_MSVC_VERSION_INTERNAL = Config.MSVC_VERSION_INTERNAL
+class Patch:
+
+    class vc:
+
+        class _VCVER:
+
+            _VCVER = vc._VCVER
+
+            @classmethod
+            def enable_copy(cls):
+                hook = list(cls._VCVER)
+                vc._VCVER = hook
+                return hook
+
+            @classmethod
+            def restore(cls):
+                vc._VCVER = cls._VCVER
+
+    class Config:
+
+        class MSVC_VERSION_INTERNAL:
+
+            MSVC_VERSION_INTERNAL = Config.MSVC_VERSION_INTERNAL
+
+            @classmethod
+            def enable_copy(cls):
+                hook = dict(cls.MSVC_VERSION_INTERNAL)
+                Config.MSVC_VERSION_INTERNAL = hook
+                return hook
+
+            @classmethod
+            def restore(cls):
+                Config.MSVC_VERSION_INTERNAL = cls.MSVC_VERSION_INTERNAL
 
 class ConfigTests(unittest.TestCase):
 
     def test_vcver(self):
         # all vc._VCVER in Config.MSVC_VERSION_SUFFIX
-        _ADD_VCVER = list(_VCVER)
-        _ADD_VCVER.append('99.9')
-        vc._VCVER = _ADD_VCVER
+        _VCVER = Patch.vc._VCVER.enable_copy()
+        _VCVER.append('99.9')
         with self.assertRaises(MSVCInternalError):
             Config.verify()
-        vc._VCVER = _VCVER
+        Patch.vc._VCVER.restore()
 
     def test_msvc_version_internal(self):
         # all vc._VCVER numstr in Config.MSVC_VERSION_INTERNAL
-        _DEL_MSVC_VERSION_INTERNAL = dict(_MSVC_VERSION_INTERNAL)
-        del _DEL_MSVC_VERSION_INTERNAL['14.3']
-        Config.MSVC_VERSION_INTERNAL = _DEL_MSVC_VERSION_INTERNAL
+        MSVC_VERSION_INTERNAL = Patch.Config.MSVC_VERSION_INTERNAL.enable_copy()
+        del MSVC_VERSION_INTERNAL['14.3']
         with self.assertRaises(MSVCInternalError):
             Config.verify()
-        Config.MSVC_VERSION_INTERNAL = _MSVC_VERSION_INTERNAL
+        Patch.Config.MSVC_VERSION_INTERNAL.restore()
 
     def test_verify(self):
         Config.verify()