Consider North Carolina tested.

Consider North Carolina sorely tested. And better for it.

Clemson coach Oliver Purnell called Sunday night’s meeting with the top-ranked Tar Heels, the ACC opener for both clubs, “a measuring stick” for his 19th-ranked Tigers. For North Carolina, too, this was a chance to prove its mettle after subsisting on a steady diet of opponents who inevitably wilted before matters got serious.

The Tar Heels had won their first 14 games, handily maintaining membership in college basketball’s fast-diminishing group of undefeated teams. But not one of their pre-ACC opponents ranked among the nation’s top 25. Only at Ohio State in late November had the Heels previously even trailed at halftime.

Clemson, meanwhile, has inched steadily toward heightened respectability under Purnell. But his Tigers are dogged by history – the program has long held a reputation for padding its resume with modestly challenging opponents, only to melt like ice in a hot gym once ACC play began.

That may be changing. From opening tap to final buzzer, the North Carolina-Clemson clash was marked by two fleet, athletic, aggressive teams that went at each other with rare, unflagging competitive ferocity. Fittingly, play extended to overtime. Fittingly, the outcome was decided on a dramatic final shot, a 3-pointer delivered by UNC’s Wayne Ellington to secure a 90-88 victory at Littlejohn Coliseum.

“Clemson is by far the best team that we have played,” North Carolina coach Roy Williams said. “It was the first team we’ve really been tested by this year.”

The outcome was not decided until one sophomore, Clemson’s David Potter, betrayed what had been a sterling defensive performance by trying for a steal while guarding Ellington, another sophomore who already had a career-best 33 points.

“In fact, 33 would have been fine,” Purnell said. The Tigers had picked their poison, limiting UNC’s star center Tyler Hansborough to seven field goal attempts, with half of his dozen points coming at the foul line.

But Potter’s lunge left Ellington with a clear look at the basket from the left wing. His 3-pointer with .4 seconds remaining not only capped a 36-point performance, but provided a measure of redemption for his miss the last time the Heels were extended to overtime – a loss to Georgetown in last year’s NCAA regional finals.

“When I recruited Wayne Ellington I thought this could be perhaps the best scorer I’ve ever recruited,” Williams said. “He had a chance to be a hero (against the Hoyas). He had another chance tonight. And he made this one. This one, because it was at the end of the game and the end of overtime, was bigger.”

Williams had worried aloud about his team’s depth prior to visiting Clemson. An unseasonably warm day, an unusually determined and able opponent, foul trouble, and an extra period all conspired to bring the coach’s worst fears to fruition.

Injured Bobby Frasor, the logical replacement, sat toward the end of the bench wearing a suit, unable to play when Ty Lawson drew two fouls in the game’s first 10 minutes. So Williams ventured significant playing time for playmaker Quentin Thomas. That didn’t work – the senior had three turnovers and no assists in the eight minutes he played. Will Graves came off the bench to miss four shots in four tries. Mike Copeland appeared briefly.

That left six players to weather the storm as Clemson forced 19 turnovers, blocked 11 shots, gained 11 steals, and held North Carolina, the ACC’s best shooting team, to 41.7 percent accuracy. The Tigers led 41-38 at halftime, and had three shots in the lane to win at the end of regulation.

Clemson's onslaught, fueled in part by a packed house of 10,000 screaming fans -- many wearing orange T-shirts proclaiming membership in “Oliver Purnell’s Posse” -- would have swept away most teams. But not the Heels, who persisted because they, too, attacked at both ends. “We want to attack all the time,” Williams said.

One area where Clemson could not escape its worst nature was at the foul line. In falling to 12-2, the Tigers missed three of their last four free throws in regulation, including the front ends of a pair of one-and-one opportunities. Overall they converted 51.9 percent of 27 foul shots, allowing North Carolina to escape with its first victory in eight overtime contests dating to 2003, Matt Doherty’s last year as head coach.

In the process Ellington and the Heels erased a bit of the sour taste left by their most recent defeat, now more than nine months past, a memory that served as prod and inspiration from the moment they began preparation for this season.