replace module unit test coverage

Also fixed file closing after reading.

Change-Id: I8485fd35a2c7346ef2d38ffd7278fdaab6dc57ad
Partial-Bug: #1365391

fuelmenu/common/replace.py

@@ -16,7 +16,8 @@ import re
 
 
 def replaceInFile(filename, orig, new):
-    lines = open(filename).readlines()
+    with open(filename) as f:
+        lines = f.readlines()
     for lineno, line in enumerate(lines):
         lines[lineno] = re.sub(orig, new, line)
     with open(filename, 'w') as f:

fuelmenu/tests/test_common_replace.py

@@ -0,0 +1,47 @@
+# Copyright 2016 Mirantis, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import mock
+import unittest
+
+from fuelmenu.common import replace
+
+
+def custom_mock_open(lines):
+    """Customizing mock open
+
+    :param lines: list of lines
+    :return: mock object
+    """
+    m_open = mock.mock_open()
+    m_open.return_value.readlines.return_value = [
+        '{}\n'.format(line) for line in lines
+    ]
+    return m_open
+
+
+class TestReplace(unittest.TestCase):
+    def setUp(self):
+        super(TestReplace, self).setUp()
+        self.data = ['line1', 'line2', 'line3']
+
+    def test_replace(self):
+        filename = 'filename'
+        with mock.patch('__builtin__.open', custom_mock_open(self.data)) \
+                as m_open:
+            replace.replaceInFile(filename, 'line2', 'line4')
+            self.assertEqual(m_open.call_args_list,
+                             [mock.call(filename), mock.call(filename, 'w')])
+            m_open.return_value.write.assert_called_once_with(
+                'line1\nline4\nline3\n')