Get mock coverage back to 100% (GH-18228)

* use the `: pass` and `: yield` patterns for code that isn't expected to ever be executed.

* The _Call items passed to _AnyComparer are only ever of length two, so assert instead of if/else

* fix typo

* Fix bug, where stop-without-start patching dict blows up with `TypeError: 'NoneType' object is not iterable`, highlighted by lack of coverage of an except branch.

* The fix for bpo-37972 means _Call.count and _Call.index are no longer needed.

* add coverage for calling next() on a mock_open with readline.return_value set.

* __aiter__ is defined on the Mock so the one on _AsyncIterator is never called.

1 files changed, 8 insertions, 0 deletions

diff --git a/Lib/unittest/test/testmock/testpatch.py b/Lib/unittest/test/testmock/testpatch.py
index 438dfd8cfb..f1bc0e1cd4 100644
--- a/Lib/unittest/test/testmock/testpatch.py
+++ b/Lib/unittest/test/testmock/testpatch.py
@@ -770,6 +770,14 @@ class PatchTest(unittest.TestCase):
         self.assertEqual(d, original)
 
 
+    def test_patch_dict_stop_without_start(self):
+        d = {'foo': 'bar'}
+        original = d.copy()
+        patcher = patch.dict(d, [('spam', 'eggs')], clear=True)
+        self.assertEqual(patcher.stop(), False)
+        self.assertEqual(d, original)
+
+
     def test_patch_dict_class_decorator(self):
         this = self
         d = {'spam': 'eggs'}