Added a test.

tests/functional/openlp_plugins/presentations/test_messagelistener.py

@@ -26,6 +26,7 @@ from unittest import TestCase
 
 from openlp.core.common import Registry
 from openlp.plugins.presentations.lib.mediaitem import MessageListener, PresentationMediaItem
+from openlp.plugins.presentations.lib.messagelistener import Controller
 from tests.functional import patch, MagicMock
 from tests.helpers.testmixin import TestMixin
 
@@ -124,3 +125,26 @@ class TestMessageListener(TestCase, TestMixin):
 
         # THEN: The handler should be set to None
         self.assertIsNone(ml.handler, 'The handler should be None')
+
+
+class TestController(TestCase, TestMixin):
+    """
+    Test the Presentation Controller.
+    """
+
+    def add_handler_failure_test(self):
+        """
+        Test that add_handler does set doc.slidenumber to 0 in case filed loading
+        """
+        # GIVEN: A Controller, a mocked doc-controller
+        controller = Controller(True)
+        mocked_doc_controller = MagicMock()
+        mocked_doc = MagicMock()
+        mocked_doc.load_presentation.return_value = False
+        mocked_doc_controller.add_document.return_value = mocked_doc
+
+        # WHEN: calling add_handler that fails
+        controller.add_handler(mocked_doc_controller, MagicMock(), True, 0)
+
+        # THEN: slidenumber should be 0
+        self.assertEqual(controller.doc.slidenumber, 0, 'doc.slidenumber should be 0')