def METHOD_NAME(self):
    col1 = DataTablesColumn(name='test-column1', span=2)
    col2 = DataTablesColumn(name='test-column2', span=3)
    group = DataTablesColumnGroup('test-group')
    group.add_column(col1)
    group.add_column(col2)
    self.assertEqual(group.render_html, '<th class="col-sm-5" colspan="2"><strong>test-group</strong></th>')