split lines the same when read from stdin

tests/integration/test_main.py

@@ -51,6 +51,29 @@ index d64ac39..7d943de 100644
     assert err == ''
 
 
+def test_form_feed_line_split(tmpdir, capsys):
+    """Test that form feed is treated the same for stdin."""
+    src = 'x=1\n\f\ny=1\n'
+    expected_out = '''\
+t.py:1:2: E225 missing whitespace around operator
+t.py:3:2: E225 missing whitespace around operator
+'''
+
+    with tmpdir.as_cwd():
+        tmpdir.join('t.py').write(src)
+
+        with mock.patch.object(utils, 'stdin_get_value', return_value=src):
+            _call_main(['-', '--stdin-display-name=t.py'], retv=1)
+            out, err = capsys.readouterr()
+            assert out == expected_out
+            assert err == ''
+
+        _call_main(['t.py'], retv=1)
+        out, err = capsys.readouterr()
+        assert out == expected_out
+        assert err == ''
+
+
 def test_e101_indent_char_does_not_reset(tmpdir, capsys):
     """Ensure that E101 with an existing indent_char does not reset it."""
     t_py_contents = """\

tests/unit/test_file_processor.py

@@ -89,20 +89,15 @@ def test_should_ignore_file_to_handle_disable_noqa(default_options):
 @mock.patch('flake8.utils.stdin_get_value')
 def test_read_lines_from_stdin(stdin_get_value, default_options):
     """Verify that we use our own utility function to retrieve stdin."""
-    stdin_value = mock.Mock()
-    stdin_value.splitlines.return_value = []
-    stdin_get_value.return_value = stdin_value
+    stdin_get_value.return_value = ''
     processor.FileProcessor('-', default_options)
     stdin_get_value.assert_called_once_with()
-    stdin_value.splitlines.assert_called_once_with(True)
 
 
 @mock.patch('flake8.utils.stdin_get_value')
 def test_stdin_filename_attribute(stdin_get_value, default_options):
     """Verify that we update the filename attribute."""
-    stdin_value = mock.Mock()
-    stdin_value.splitlines.return_value = []
-    stdin_get_value.return_value = stdin_value
+    stdin_get_value.return_value = ''
     file_processor = processor.FileProcessor('-', default_options)
     assert file_processor.filename == 'stdin'
 
@@ -111,9 +106,7 @@ def test_stdin_filename_attribute(stdin_get_value, default_options):
 def test_read_lines_uses_display_name(stdin_get_value, default_options):
     """Verify that when processing stdin we use a display name if present."""
     default_options.stdin_display_name = 'display_name.py'
-    stdin_value = mock.Mock()
-    stdin_value.splitlines.return_value = []
-    stdin_get_value.return_value = stdin_value
+    stdin_get_value.return_value = ''
     file_processor = processor.FileProcessor('-', default_options)
     assert file_processor.filename == 'display_name.py'
 
@@ -123,9 +116,7 @@ def test_read_lines_ignores_empty_display_name(
         stdin_get_value, default_options,
 ):
     """Verify that when processing stdin we use a display name if present."""
-    stdin_value = mock.Mock()
-    stdin_value.splitlines.return_value = []
-    stdin_get_value.return_value = stdin_value
+    stdin_get_value.return_value = ''
     default_options.stdin_display_name = ''
     file_processor = processor.FileProcessor('-', default_options)
     assert file_processor.filename == 'stdin'