diff -r 09b88b5bebd0 Doc/library/test.rst
--- a/Doc/library/test.rst	Tue May 28 12:50:54 2013 +0300
+++ b/Doc/library/test.rst	Tue May 28 14:42:18 2013 +0300
@@ -362,6 +362,34 @@
       New optional arguments *filters* and *quiet*.
 
 
+.. function:: captured_stderr()
+
+   A context manager that runs the :keyword:`with` statement body using a
+   :class:`io.StringIO` object as sys.stderr.  That object can be retrieved
+   using the ``as`` clause of the :keyword:`with` statement.
+
+   Example use::
+
+      with captured_stderr() as s:
+          print("hello", file=sys.stderr)
+      assert s.getvalue() == "hello\n"
+
+
+.. function:: captured_stdin()
+
+   A context manager that runs the :keyword:`with` statement body using a
+   :class:`io.StringIO` object as sys.stdin.  That object can be retrieved
+   using the ``as`` clause of the :keyword:`with` statement.
+
+   Example use::
+
+      with support.captured_stdin() as s:
+          s.write('hello\n')
+          s.seek(0)
+          captured = input()
+      self.assertEqual(captured, "hello")
+
+
 .. function:: captured_stdout()
 
    A context manager that runs the :keyword:`with` statement body using a
diff -r 09b88b5bebd0 Lib/test/support.py
--- a/Lib/test/support.py	Tue May 28 12:50:54 2013 +0300
+++ b/Lib/test/support.py	Tue May 28 14:42:18 2013 +0300
@@ -1181,14 +1181,28 @@
 
        with captured_stdout() as s:
            print("hello")
-       self.assertEqual(s.getvalue(), "hello")
+       self.assertEqual(s.getvalue(), "hello\n")
     """
     return captured_output("stdout")
 
 def captured_stderr():
+    """Capture the output of sys.stderr:
+
+       with captured_stderr() as s:
+           print("hello", file=sys.stderr)
+       self.assertEqual(s.getvalue(), "hello\n")
+    """
     return captured_output("stderr")
 
 def captured_stdin():
+    """Capture the input of sys.stdin:
+
+       with support.captured_stdin() as s:
+           s.write('hello\n')
+           s.seek(0)
+           captured = input()
+       self.assertEqual(captured, "hello")
+    """
     return captured_output("stdin")
 
 
diff -r 09b88b5bebd0 Lib/test/test_support.py
--- a/Lib/test/test_support.py	Tue May 28 12:50:54 2013 +0300
+++ b/Lib/test/test_support.py	Tue May 28 14:42:18 2013 +0300
@@ -141,8 +141,10 @@
 
     def test_captured_stdin(self):
         with support.captured_stdin() as s:
-            print("hello", file=sys.stdin)
-        self.assertEqual(s.getvalue(), "hello\n")
+            s.write('hello\n')
+            s.seek(0)
+            captured = input()
+        self.assertEqual(captured, "hello")
 
     def test_gc_collect(self):
         support.gc_collect()