No. 18 Central Florida had not been tested, winning each of its first seven games by double figures, including several blowouts.

The Knights have been tested now, and they passed.

Adrian Killins Jr. scored on two long touchdown runs, and unbeaten UCF survived a stern challenge from SMU in a 31-24 win Saturday at Gerald J. Ford Stadium in Dallas, Texas.

The Knights improved to 8-0 for the first time in school history, but it wasn't easy.

"We made it harder than it probably had to be. I give a ton of credit for that to them," UCF coach Scott Frost told the Orlando Sentinel. "We found ourselves in a close game that we probably shouldn't have been in and I love the way our team responded, particularly on defense.

Killins had 145 yards on 14 carries, including a 64-yard touchdown run that put the Knights in front 28-17 midway through the third quarter.

SMU would not go away and cut the UCF lead to 28-24 heading into the fourth quarter. Xavier Jones' 2-yard run capped an 11-play, 93-yard scoring drive for the Mustangs.

Time after time, SMU drove inside UCF territory only to come up empty. Down 31-24 with 5:26, the Mustangs were at the Knights' 38-yard line, but turned it over on fourth down.

SMU would get one more chance to mount a drive for a tying touchdown in the fourth quarter. But on fourth down, SMU quarterback Ben Hicks' pass fell incomplete, and the Knights (8-0, 5-0) ran out the clock on another American Athletic Conference win.

"Our kids found a way at the end. We were in a situation this time where our defense had to go out and get a stop and we stumbled on offense and they had to get another stop," Frost told the Sentinel. "It shows a lot of heart for those kids to do what they did."

While the Mustangs' offense was not its normal potent self, the defense made big plays to keep SMU in the game into the fourth quarter. SMU defensive back Jordan Wyatt returned an interception for a touchdown and forced a fumble inside the 10-yard line to thwart a UCF drive.

"I think that's the best effort we've seen defensively," SMU coach Chad Morris said. "That was much needed from a defensive standpoint. Their want-to had to prevail. We knew it was going to take a great, collective effort. It showed tonight. We came up on the short end, but our kids played extremely hard. If we'll keep doing that, we'll be good."

UCF quarterback McKenzie Milton 23 of 40 passes for a career-high 412 yards with a touchdown and two interceptions.

Hicks completed 27 of 51 passes for 283 yards and one touchdown. Jones had 84 yards rushing and the touchdown for the Mustangs (6-3, 3-2 AAC).

The SMU defense stopped UCF on fourth down deep inside the Mustangs' territory on the Knights' first drive.

On the next play after the early stop, Hicks threw an 86-yard touchdown pass to James Proche to give SMU the early momentum and open the scoring in what would be a back-and-forth first half.

Milton tied the score on a 9-yard touchdown run and followed it on UCF's next drive with an 80-yard touchdown pass to Gabriel Davis that gave the Knights their first lead at 14-7 early in the second quarter. The 80-yard touchdown pass was the longest of Milton's career.

But Milton also threw a pair of picks in the first half. The second one was returned 36 yards for a tying touchdown by Wyatt midway through the second quarter.

Milton responded by leading another scoring drive, with Killins Jr. breaking free on a 34-yard touchdown run that sent the Knights into halftime with a 21-14 lead.

It was a hard-fought loss for the Mustangs, who came from behind to beat Tulsa last week to become bowl eligible for the first time since 2012. But Morris, who like Frost is emerging a coveted head coaching prospect, said he isn't in to moral victories.

"Regardless of the outcome of tonight's game, we still control our own destiny in our division," Morris said. We still have to play Memphis, Navy and Tulane. If you can win out, you win your side and get a chance to play these guys again. We have to keep that want to, desire and drive that we showed tonight the rest of the year."

NOTES: Central Florida coach Scott Frost, whose wife is expecting the birth of their first child at any moment, had a plane on stand-by in case the call came during the game. ... SMU entered the game with 62 plays of over 20 yards this season, the second-most in the nation. ... UCF entered the game leading the nation in scoring, averaging 51 points per game. ... Central Florida returns home next week to host Connecticut. ... SMU travels to Navy.