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, 5 insertions, 0 deletions

diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 677346725b..9b9e066cc5 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1868,6 +1868,11 @@ class MockTest(unittest.TestCase):
         with self.assertRaises(StopIteration):
             next(f1)
 
+    def test_mock_open_next_with_readline_with_return_value(self):
+        mopen = mock.mock_open(read_data='foo\nbarn')
+        mopen.return_value.readline.return_value = 'abc'
+        self.assertEqual('abc', next(mopen()))
+
     def test_mock_open_write(self):
         # Test exception in file writing write()
         mock_namedtemp = mock.mock_open(mock.MagicMock(name='JLV'))