Britney Spears Britney Spears

The No. 1 thing you need to do to become Britney Spears' dancer? Do No. 1.

Taking necessary measures to ensure the recovering pop songstress stays on track, Spears' handlers have requested all of the movers and shakers on her upcoming Circus tour submit to a drug test, E! News reports.

"They all had to be drug tested and, if they didn't pass, they were fired," a source says. "I think they only do it for her because she is under strict watch. I think they just want good influences around her."

Although drug testing may sound like no biggie as a pre-requisite for a job, it is actually not common practice in the music world (surprise!), the insider says.

Robert Baker, studio director at North Hollywood's Millennium Dance Complex, where Spears rehearses, concurs drug testing is not the norm, "but each artist is different."

"Everyone is just trying to safeguard against any foreseeable problems," Baker says.

Spears' tour, The Circus Starring: Britney Spears, kicks off March 9 in New Orleans.