diff -r 8c8315bac6a8 Lib/unittest/mock.py
--- a/Lib/unittest/mock.py	Sun Apr 20 09:45:00 2014 -0700
+++ b/Lib/unittest/mock.py	Tue Apr 22 08:58:02 2014 +0530
@@ -1894,7 +1894,7 @@
     formatted_args = ''
     args_string = ', '.join([repr(arg) for arg in args])
     kwargs_string = ', '.join([
-        '%s=%r' % (key, value) for key, value in kwargs.items()
+        '%s=%r' % (key, value) for key, value in sorted(kwargs.items())
     ])
     if args_string:
         formatted_args = args_string
diff -r 8c8315bac6a8 Lib/unittest/test/testmock/testmock.py
--- a/Lib/unittest/test/testmock/testmock.py	Sun Apr 20 09:45:00 2014 -0700
+++ b/Lib/unittest/test/testmock/testmock.py	Tue Apr 22 08:58:02 2014 +0530
@@ -1206,6 +1206,12 @@
         with self.assertRaises(AssertionError):
             m.hello.assert_not_called()
 
+    #Issue21256
+    def test_sorted_call_signature(self):
+        m = Mock()
+        m.hello(name='hello', daddy='hero')
+        text = "call(daddy='hero', name='hello')"
+        self.assertEquals(repr(m.hello.call_args), text)
 
     def test_mock_add_spec(self):
         class _One(object):
diff -r 8c8315bac6a8 Misc/NEWS
--- a/Misc/NEWS	Sun Apr 20 09:45:00 2014 -0700
+++ b/Misc/NEWS	Tue Apr 22 08:58:02 2014 +0530
@@ -54,6 +54,9 @@
 Library
 -------
 
+- Issue #21256: Call signature argument returns a sorted list.
+  This will help to write doc tests.
+
 - Issue #15002: urllib.response object to use _TemporaryFileWrapper (and
   _TemporaryFileCloser) facility. Provides a better way to handle file
   descriptor close. Patch contributed by Christian Theune.