'Add split test to vertical #`number`.
If `group_configuration_metadata` is not None, use it to assign group configuration to split test.'

def _add_split_test_to_vertical(self, number, group_configuration_metadata=None):

    vertical = self.course_fixture.get_nested_xblocks(category='vertical')[number]
    if group_configuration_metadata:
        split_test = XBlockFixtureDesc('split_test', 'Test    Content    Experiment', metadata=group_configuration_metadata)
    else:
        split_test = XBlockFixtureDesc('split_test', 'Test    Content    Experiment')
    self.course_fixture.create_xblock(vertical.locator, split_test)
    return split_test
