Unit-testing models Codeigniter

I'm new to unit-testing, so this is maybe a little dumb question. Imagine, we have a simple model method.

model

public function admin_anc(){

       $rows = $this->db
            ->select('u.*,s.name,')
            ->select('COUNT(c.id_budget) AS ref_campaign_count', FALSE)
            ->select('SUM(c.) AS sum_est', FALSE)
            ->from(' u')
            ->join(' c', 'u.id = c.id_budget', 'left')
            ->join('s', 'u.id_gab=s.id','left')
            ->group_by('u.id', 'u.name', 'u.pr')
            ->get()
            ->result_array();
            return $rows;

    }

Thanks.