AtomEntityProvider ser = createAtomEntityProvider();
Map<String, Object> localRoomData = new HashMap<String, Object>(roomData);
String mediaResourceSourceKey = "~src";
localRoomData.put(mediaResourceSourceKey, "http://localhost:8080/images/image1");
EdmEntitySet roomsSet = MockFacade.getMockEdm().getDefaultEntityContainer().getEntitySet("Rooms");
EdmEntityType roomType = roomsSet.getEntityType();
EdmMapping mapping = mock(EdmMapping.class);
when(roomType.getMapping()).thenReturn(mapping);
when(mapping.getMediaResourceSourceKey()).thenReturn(mediaResourceSourceKey);
ODataResponse response = ser.writeEntry(roomsSet, localRoomData, DEFAULT_PROPERTIES);
String xmlString = verifyResponse(response);