Nina Dobrev And Ian Somerhalder’s Relationship: What Was The Test She Gave Her ‘Vampire Diaries’ Co-Star?

"Vampire Diaries" co-stars Nina Dobrev, 23, and Ian Somerhalder, 33, are inseparable. The pair are spotted at red carpets and festivals and never stop gushing about each other in interviews. Shockingly, Dobrev revealed in September that she initially didn't want to be dating her co-star. So, how did Dobrev and Somerhalder make it this far in their relationship?

Dobrev explained in the Nov. 2012 issue of Self magazine that she had a relationship test that Somerhalder had to pass. 

"He has to be a happy person," Dobrev said of her dating requirement. "You'll laugh and enjoy life more."

Somerhalder being a happy person has also helped Dobrev with her stress levels. "The Vampire Diaries" actress tells the magazine that her beau, yoga and chocolate all help to lower any stress she's feeling. 

As mentioned earlier though, Somerhalder actually was a former stress factor for the actress. Dobrev said that she fought her attraction for her co-star for a "really, really long time," but explained to Seventeen magazine that "sometimes you can't help who you have a connection with."

Dobrev had told the magazine in 2009 that she wouldn't ever date any of her co-stars, but told Seventeen this past October that, "it was honestly what i believed at the time."

"The Vampire Diaries" premiered in 2009. Nina Dobrev plays teen Elena Gilbert on the CW drama, and has some serious on-screen sexual tension with Ian Somerhalder, who plays Damon Salvatore. The duo aren't exactly love birds though. Despite a steamy kiss in episode 19 of season three, Elena and Damon are in a love triangle...with Damon's brother Stefan (Paul Wesley). 

"The Vampire Diaries" just began its fourth season on Oct. 11. Off-Screen the pair have been dating for almost almost two years.