Credit: Steve Granitz/

Yep, he did it -- and it wasn't so bad!

As previously reported by Us Weekly, Justin Bieber submitted to a DNA test last Friday to disprove, once and for all, Mariah Yeater's claims that he fathered her son Tristyn, 4 months.

"Yeah, I took it," Bieber, 17, said of the test during an appearance on The Late Show with David Letterman, airing Wednesday. The procedure was simple, the pop singer explained. "They just swab your mouth."

David Letterman wondered whether the "Baby, Baby" singer was knocked unconscious or "disrobed" for the procedure. "I don't think so!" Bieber joked.

The ball is now in the court of Yeater, 20, who must provide a DNA sample from her little boy to see whether it matches that of Bieber. In a paternity suit dropped last week, Yeater claimed she had a 30-second sexual encounter with Bieber backstage at an L.A. concert in October 2010, giving birth to Tristyn 9 months later.

"I could smell a weasel," Bieber (currently going strong with girlfriend Selena Gomez) told Letterman of Yeater's outrageous suit. "It's gonna happen. Being in the spotlight, people can say whatever."