diff --git a/Lib/test/test_unittest.py b/Lib/test/test_unittest.py
index 108802d..120a90d 100644
--- a/Lib/test/test_unittest.py
+++ b/Lib/test/test_unittest.py
@@ -2510,6 +2510,18 @@
         self.assertIsNot(thing, object())
         self.assertRaises(self.failureException, self.assertIsNot, thing, thing)
 
+    def testAssertIsInstance(self):
+        thing = []
+        self.assertIsInstance(thing, list)
+        self.assertRaises(self.failureException, self.assertIsInstance,
+                          thing, dict)
+
+    def testAssertNotIsInstance(self):
+        thing = []
+        self.assertNotIsInstance(thing, dict)
+        self.assertRaises(self.failureException, self.assertNotIsInstance,
+                          thing, list)
+
     def testAssertIn(self):
         animals = {'monkey': 'banana', 'cow': 'grass', 'seal': 'fish'}
 
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index 660ddeb..88254be 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -620,8 +620,9 @@
                 except (TypeError, IndexError, NotImplementedError):
                     differing += ('Unable to index element %d '
                                   'of second %s\n' % (len1, seq_type_name))
-        standardMsg = differing + '\n' + '\n'.join(difflib.ndiff(pprint.pformat(seq1).splitlines(),
-                                            pprint.pformat(seq2).splitlines()))
+        standardMsg = differing + '\n' + '\n'.join(
+            difflib.ndiff(pprint.pformat(seq1).splitlines(),
+                          pprint.pformat(seq2).splitlines()))
         msg = self._formatMessage(msg, standardMsg)
         self.fail(msg)
 
@@ -734,7 +735,8 @@
             if key not in actual:
                 missing.append(key)
             elif value != actual[key]:
-                mismatched.append('%s, expected: %s, actual: %s' % (key, value,                                                                                                       actual[key]))
+                mismatched.append('%s, expected: %s, actual: %s' %
+                                  (key, value, actual[key]))
 
         if not (missing or mismatched):
             return
@@ -793,7 +795,8 @@
                 'Second argument is not a string'))
 
         if first != second:
-            standardMsg = '\n' + ''.join(difflib.ndiff(first.splitlines(True), second.splitlines(True)))
+            standardMsg = '\n' + ''.join(difflib.ndiff(first.splitlines(True),
+                                                       second.splitlines(True)))
             self.fail(self._formatMessage(msg, standardMsg))
 
     def assertLess(self, a, b, msg=None):
@@ -832,6 +835,19 @@
             standardMsg = 'unexpectedly None'
             self.fail(self._formatMessage(msg, standardMsg))
 
+    def assertIsInstance(self, obj, cls, msg=None):
+        """Same as self.assertTrue(isinstance(obj, cls)), with a nicer
+        default message."""
+        if not isinstance(obj, cls):
+            standardMsg = '%r is not an instance of %r' % (obj, cls)
+            self.fail(self._formatMessage(msg, standardMsg))
+
+    def assertNotIsInstance(self, obj, cls, msg=None):
+        """Included for symmetry with assertIsInstance."""
+        if isinstance(obj, cls):
+            standardMsg = '%r is an instance of %r' % (obj, cls)
+            self.fail(self._formatMessage(msg, standardMsg))
+
     def assertRaisesRegexp(self, expected_exception, expected_regexp,
                            callable_obj=None, *args, **kwargs):
         """Asserts that the message in a raised exception matches a regexp.