R&B singer Chris Brown has tested positive for marijuana - a Los Angeles judge has set a hearing to decide whether he violated his probation stemming from a 2009 assault on then-girlfriend Rihanna.br br According to a report presented in court, Brown tested positive in June in his home state of Virginia, where he is fulfilling his community service.br br Brown was placed on probation and given six months of community service after pleading guilty to criminal assault for beating Rihanna on the eve of the Grammy awards in 2009.