bpo-17185: Add __signature__ to mock that can be used by inspect for signature (GH11048)

* Fix partial and partial method signatures in mock

* Add more calls

* Add NEWS entry

* Use assertEquals and fix markup in NEWS

* Refactor branching and add markup reference for functools

* Revert partial object related changes and fix pr comments

Lib/unittest/test/testmock/testhelpers.py

@@ -1,3 +1,4 @@
+import inspect
 import time
 import types
 import unittest
@@ -901,6 +902,35 @@ class SpecSignatureTest(unittest.TestCase):
         self.assertFalse(hasattr(autospec, '__name__'))
 
 
+    def test_spec_inspect_signature(self):
+
+        def myfunc(x, y):
+            pass
+
+        mock = create_autospec(myfunc)
+        mock(1, 2)
+        mock(x=1, y=2)
+
+        self.assertEqual(inspect.getfullargspec(mock), inspect.getfullargspec(myfunc))
+        self.assertEqual(mock.mock_calls, [call(1, 2), call(x=1, y=2)])
+        self.assertRaises(TypeError, mock, 1)
+
+
+    def test_spec_inspect_signature_annotations(self):
+
+        def foo(a: int, b: int=10, *, c:int) -> int:
+            return a + b + c
+
+        mock = create_autospec(foo)
+        mock(1, 2, c=3)
+        mock(1, c=3)
+
+        self.assertEqual(inspect.getfullargspec(mock), inspect.getfullargspec(foo))
+        self.assertEqual(mock.mock_calls, [call(1, 2, c=3), call(1, c=3)])
+        self.assertRaises(TypeError, mock, 1)
+        self.assertRaises(TypeError, mock, 1, 2, 3, c=4)
+
+
 class TestCallList(unittest.TestCase):
 
     def test_args_list_contains_call_list(self):