bpo-37212: Preserve keyword argument order in unittest.mock.call and error messages

Lib/unittest/mock.py

@@ -2281,7 +2281,7 @@ def _format_call_signature(name, args, kwargs):
     formatted_args = ''
     args_string = ', '.join([repr(arg) for arg in args])
     kwargs_string = ', '.join([
-        '%s=%r' % (key, value) for key, value in sorted(kwargs.items())
+        '%s=%r' % (key, value) for key, value in kwargs.items()
     ])
     if args_string:
         formatted_args = args_string

Lib/unittest/test/testmock/testmock.py

@@ -1512,11 +1512,11 @@ def test_assert_called_once_message_not_called(self):
             m.assert_called_once()
         self.assertNotIn("Calls:", str(e.exception))
 
-    #Issue21256 printout of keyword args should be in deterministic order
-    def test_sorted_call_signature(self):
+    #Issue37212 printout of keyword args now preserves the original order
+    def test_ordered_call_signature(self):
         m = Mock()
         m.hello(name='hello', daddy='hero')
-        text = "call(daddy='hero', name='hello')"
+        text = "call(name='hello', daddy='hero')"
         self.assertEqual(repr(m.hello.call_args), text)
 
     #Issue21270 overrides tuple methods for mock.call objects

Misc/NEWS.d/next/Library/2019-06-22-22-00-35.bpo-37212.Zhv-tq.rst

@@ -0,0 +1,2 @@
+:func:`unittest.mock.call` now preserves the order of keyword arguments in
+repr output. Patch by Karthikeyan Singaravelan.