diff -r a15d65d8f269 Lib/unittest/case.py
--- a/Lib/unittest/case.py	Sat Mar 26 14:48:04 2011 +0100
+++ b/Lib/unittest/case.py	Sat Mar 26 14:57:54 2011 -0300
@@ -267,6 +267,10 @@
 
     _classSetupFailed = False
 
+    # List of patched objects
+
+    _patched = []
+
     def __init__(self, methodName='runTest'):
         """Create an instance of the class that will use the named test
            method when executed. Raises a ValueError if the instance does
@@ -443,6 +447,8 @@
                 self._executeTestPart(self.tearDown, outcome)
 
             self.doCleanups()
+            self.unpatch_all()
+            
             if outcome.success:
                 result.addSuccess(self)
             else:
@@ -490,6 +496,17 @@
         # even though we no longer us it internally
         return outcome.success
 
+    def patch(self, obj, attr, value):
+        """ Patch an object for the current test """
+        self._patched.append((obj, attr, getattr(obj, attr)))
+        setattr(obj, attr, value)
+
+    def unpatch_all(self):
+        """ Restore all patched objects to the previous state """
+        for obj, attr, value in self._patched:
+            setattr(obj, attr, value)
+        self._patched = []
+
     def __call__(self, *args, **kwds):
         return self.run(*args, **kwds)
 
diff -r a15d65d8f269 Lib/unittest/test/test_case.py
--- a/Lib/unittest/test/test_case.py	Sat Mar 26 14:48:04 2011 +0100
+++ b/Lib/unittest/test/test_case.py	Sat Mar 26 14:57:54 2011 -0300
@@ -372,6 +372,25 @@
         # ... and nothing should happen
         Foo().tearDown()
 
+    def test_patch(self):
+
+        class Bar(object):
+            def foo(self):
+                return 42
+
+        class PatchTest(unittest.TestCase):
+            pass
+
+        bar = Bar()
+        patch_test = PatchTest()
+        self.assertEqual(bar.foo(), 42)
+
+        patch_test.patch(bar, 'foo', lambda: 7)
+        self.assertEqual(bar.foo(), 7)
+
+        patch_test.unpatch_all()
+        self.assertEqual(bar.foo(), 42)
+
     # "Return a string identifying the specific test case."
     #
     # Because of the vague nature of the docs, I'm not going to lock this