Increase test coverage

Test cases for expose.py has been added to increase coverage from
86% to 100%.

Two test cases has been added with "rest_content_types" as
argument and without "rest_content_type".

Change-Id: If757f31be1b314cdac9133133a8cac6614969e81
Partial-Bug: #1511667

magnum/tests/unit/api/test_expose.py

@@ -0,0 +1,29 @@
+#    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
+
+from magnum.api import expose
+from magnum.tests import base
+
+
+class TestExpose(base.BaseTestCase):
+
+    @mock.patch('wsmeext.pecan.wsexpose')
+    def test_expose_with_rest_content_types(self, mock_pecan):
+        self.assertTrue(expose.expose(rest_content_types='json'))
+        mock_pecan.assert_called_with(rest_content_types='json')
+
+    @mock.patch('wsmeext.pecan.wsexpose')
+    def test_expose_without_rest_content_types(self, mock_pecan):
+        self.assertTrue(expose.expose())
+        mock_pecan.assert_called_once_with(rest_content_types=('json',))