Kusal Mendis and captain Dimuth Karunaratne scored half-centuries as Sri Lanka pushed to 305 for six before bad light brought stumps early on day one of the first test against New Zealand in Christchurch on Thursday.It was a positive day at the batting crease for the south Asians, who can reach the World Test Championship final if they sweep the Black Caps in the two-test series and Australia deny India victory in the fourth test in Ahmedabad.New Zealand captain Tim Southee won the toss and put his bowlers to work on a green-tinged pitch at Christchurch's Hagley Oval.But it backfired as Mendis and Karunaratne put on a 137-run stand for the second wicket.Fast bowler Southee broke the partnership by dismissing Mendis lbw for 87 from 83 balls when the number three declined to offer a shot.Southee also had opener Oshada Fernando caught down the leg-side for 13 and Dinesh Chandimal caught in the slips for 39 to be the pick of the bowlers on a frustrating day for the hosts.Number six Dhananjaya de Silva was 39 not out and tail-ender Kasun Rajitha was 16 not out when play was abandoned late in the final session.Paceman Matt Henry took two wickets, having Karunaratne (50) and all-rounder Angelo Mathews (47) each caught in the slips.He was unlucky not to have more, though, as he and Southee beat the bat repeatedly in the morning."It's always a frustrating day when you're, I suppose, beating the bat like that," said Henry."We've just got to be a little bit better for longer because there was a period there that hurt us a bit."It was a poor day for New Zealand's other seamers, with Neil Wagner conceding 68 runs in 10 wicketless overs, a major comedown after his final day heroics in the recent one-run win over England in