diff -r 39e0be9106c1 Lib/test/support.py
--- a/Lib/test/support.py	Sun May 26 18:57:00 2013 -0700
+++ b/Lib/test/support.py	Mon May 27 20:44:46 2013 +0300
@@ -1181,14 +1181,26 @@
 
        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 captured_stdin() as s:
+           print("hello", file=sys.stdin)
+       self.assertEqual(s.getvalue(), "hello\n")
+    """
     return captured_output("stdin")