2 files changed, 28 insertions, 0 deletions
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 307b8b7657a..0f30bccc9cf 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1702,6 +1702,19 @@ class MockTest(unittest.TestCase):
         self.assertEqual(lines[1], 'Norwegian Blue')
         self.assertEqual(list(f1), [])
 
+    def test_mock_open_using_next(self):
+        mocked_open = mock.mock_open(read_data='1st line\n2nd line\n3rd line')
+        f1 = mocked_open('a-name')
+        line1 = next(f1)
+        line2 = f1.__next__()
+        lines = [line for line in f1]
+        self.assertEqual(line1, '1st line\n')
+        self.assertEqual(line2, '2nd line\n')
+        self.assertEqual(lines[0], '3rd line')
+        self.assertEqual(list(f1), [])
+        with self.assertRaises(StopIteration):
+            next(f1)
+
     def test_mock_open_write(self):
         # Test exception in file writing write()
         mock_namedtemp = mock.mock_open(mock.MagicMock(name='JLV'))
diff --git a/Lib/unittest/test/testmock/testwith.py b/Lib/unittest/test/testmock/testwith.py
index 5172c222d97..42ebf3898c8 100644
--- a/Lib/unittest/test/testmock/testwith.py
+++ b/Lib/unittest/test/testmock/testwith.py
@@ -230,7 +230,22 @@ class TestMockOpen(unittest.TestCase):
         self.assertEqual(lines[1], 'bar\n')
         self.assertEqual(lines[2], 'baz\n')
         self.assertEqual(h.readline(), '')
+        with self.assertRaises(StopIteration):
+            next(h)
 
+    def test_next_data(self):
+        # Check that next will correctly return the next available
+        # line and plays well with the dunder_iter part.
+        mock = mock_open(read_data='foo\nbar\nbaz\n')
+        with patch('%s.open' % __name__, mock, create=True):
+            h = open('bar')
+            line1 = next(h)
+            line2 = next(h)
+            lines = [l for l in h]
+        self.assertEqual(line1, 'foo\n')
+        self.assertEqual(line2, 'bar\n')
+        self.assertEqual(lines[0], 'baz\n')
+        self.assertEqual(h.readline(), '')
 
     def test_readlines_data(self):
         # Test that emulating a file that ends in a newline character works