MappingDAO mockedMappingDAO = mock(MappingDAO.class);
PreviewAction previewAction = new PreviewAction();
previewAction.setMappingDAO(mockedMappingDAO);
when(mockedMappingDAO.findById((long)121)).thenReturn(mapping1);
when(mockedMappingDAO.findById((long)122)).thenReturn(mapping2);
when(mockedMappingDAO.findById((long)123)).thenReturn(mapping3);
List<ArrayList> dataList = new ArrayList<ArrayList>();
// problem : how do i make return findById the id i want?