Nassau County detective Hector Rosario wasn’t fooling anyone when he staged a fake police raid at a Long Island gambling den on behalf of the Bonanno crime family, a mob snitch testified Wednesday.

Rosario, 51, who prosecutors say “sold himself” to the mafia, was sent by a Bonanno associate to intimidate four separate gambling spots run by competing mob families, but he wasn’t particularly convincing, Bonanno turncoat Sal Russo said at Rosario’s Brooklyn Federal Court trial for obstructing governmental proceedings and lying to the FBI.

When Rosario conducted his raid on Salvatore “Sal the Shoemaker” Rubino’s Merrick shoe repair shop a decade ago, he couldn’t fool “Mario the Landscaper,” one of the gamblers sitting at a joker poker machine, Russo said.

Rubino was running the gambling parlor in the back of his shop, Sal’s Shoe Repair, for the Genovese crime family, and he was cutting into the Bonannos’ business, so Russo hatched the plan to send the cop in to scare them into shutting down, he testified.

Russo made sure to be there the day of the raid, gambling at a poker machine so no one there would think the Bonannos were involved.

Rosario stormed in with two men, Russo said, but didn’t make any arrests or seize any property.

“I just heard yelling and screaming, ‘This is the police! This is the police!’ … They broke the screen on one of the machines,” Russo recounted. “And they kept screaming, ‘This is the police!’ And they walked out.”

The gambling den’s patrons were shocked, “but one of the guys there, Mario the Landscaper, kept on saying, ‘Those are not real police. They don’t just come in breaking [things],’” Russo said. Mario’s full name hasn’t been used in the trial yet.

Rosario still got paid about $2,500, but Russo told his cop buddy that the raid didn’t seem professional. “He said, ‘I’m sorry, but I didn’t know that it was gonna go that way.’ We were a little concerned that the Genovese were gonna find out.”

He added, “A lot of things could happen … hospital, cemetery, anything.”

Rosario didn’t have luck with his other attempts at scaring off the Bonannos’ rivals, Russo said. In two instances, he showed up at the door of competitors’ gambling dens, making sure he was seen on camera as a cop, but the ruse didn’t scare the people inside into thinking they were under investigation.

In all, Rosario’s loyalty to the mob netted him maybe $8,000 overall, Russo said.

Russo also tasked him to try and shut down a gambling operation at the Gran Caffe in Lynbrook, L.I., which was funneling money to both the Bonanno and Genovese families, the mobster testified.

The Bonannos had opened up a new spot, the Soccer Club in Valley Stream, and if the Gran Caffe shut down, that would mean more customers for the new place — and they wouldn’t have to share with the Genovese family.

If that happened, Russo planned to put Rosario on the payroll at the Soccer Club and give him $1,000 or $1,500 a week, he testified.

So Rosario walked in, announced himself as a detective, and started asking for people by name — but he didn’t scare anyone into shutting down, and the Soccer Club didn’t get any new customers from his efforts, Russo said.

Rosario was paid a paltry $500 for the attempt, Russo said, adding, “I told him there was no money. The Soccer Club wasn’t making the money because all the other places didn’t shut down.”

Rosario might have gotten a $50,000 payday if one of Russo’s other schemes went through — to rob a group of Mexican heroin traffickers who were supposed to come to Hempstead to make a deal, he testified. But the deal never happened, and neither did the robbery.

Russo turned stool pigeon within a month of his November 2017 arrest for selling a kilo of cocaine to an undercover agent.

Right away, he started recording conversations with Rosario, and at the FBI’s directions, he convinced the detective to run the name of someone he said might be a cooperator through a police database. The cop obliged, scribbling the man’s address on a piece of paper.

Rosario faces 20 years on the obstruction charge and five years for lying to the FBI.