2 files changed, 25 insertions, 3 deletions
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 32703e6d7bc..976c40fc456 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1,5 +1,6 @@
 import copy
 import sys
+import tempfile
 
 import unittest
 from unittest.test.testmock.support import is_instance
@@ -1329,8 +1330,29 @@ class MockTest(unittest.TestCase):
     def test_mock_open_reuse_issue_21750(self):
         mocked_open = mock.mock_open(read_data='data')
         f1 = mocked_open('a-name')
+        f1_data = f1.read()
         f2 = mocked_open('another-name')
-        self.assertEqual(f1.read(), f2.read())
+        f2_data = f2.read()
+        self.assertEqual(f1_data, f2_data)
+
+    def test_mock_open_write(self):
+        # Test exception in file writing write()
+        mock_namedtemp = mock.mock_open(mock.MagicMock(name='JLV'))
+        with mock.patch('tempfile.NamedTemporaryFile', mock_namedtemp):
+            mock_filehandle = mock_namedtemp.return_value
+            mock_write = mock_filehandle.write
+            mock_write.side_effect = OSError('Test 2 Error')
+            def attempt():
+                tempfile.NamedTemporaryFile().write('asd')
+            self.assertRaises(OSError, attempt)
+
+    def test_mock_open_alter_readline(self):
+        mopen = mock.mock_open(read_data='foo\nbarn')
+        mopen.return_value.readline.side_effect = lambda *args:'abc'
+        first = mopen().readline()
+        second = mopen().readline()
+        self.assertEqual('abc', first)
+        self.assertEqual('abc', second)
 
     def test_mock_parents(self):
         for Klass in Mock, MagicMock:
diff --git a/Lib/unittest/test/testmock/testwith.py b/Lib/unittest/test/testmock/testwith.py
index ddcfe77e4d9..b6bfb754ad6 100644
--- a/Lib/unittest/test/testmock/testwith.py
+++ b/Lib/unittest/test/testmock/testwith.py
@@ -141,6 +141,7 @@ class TestMockOpen(unittest.TestCase):
 
     def test_mock_open_context_manager(self):
         mock = mock_open()
+        handle = mock.return_value
         with patch('%s.open' % __name__, mock, create=True):
             with open('foo') as f:
                 f.read()
@@ -148,8 +149,7 @@ class TestMockOpen(unittest.TestCase):
         expected_calls = [call('foo'), call().__enter__(), call().read(),
                           call().__exit__(None, None, None)]
         self.assertEqual(mock.mock_calls, expected_calls)
-        # mock_open.return_value is no longer static, because
-        # readline support requires that it mutate state
+        self.assertIs(f, handle)
 
     def test_mock_open_context_manager_multiple_times(self):
         mock = mock_open()