LAS VEGAS – Floyd Mayweather Jnr expects a tough test against Robert Guerrero when the pair go head to head on May 4 - but has has vowed to keep his unbeaten record intact.The pound-for-pound No 1 will defend his WBC world welterweight title at the MGM Grand in Las Vegas in his first bout since serving two months in prison for assaulting his ex-girlfriend.And Mayweather has no plans to relinquish his status as the best boxer on the planet.‘I know Guerrero has been campaigning to fight me for quite a while now and I am happy to give him his opportunity,’ he said. ‘His name is mentioned among the other great champions in boxing today and that means he has proven himself in the ring. ‘He will now have to prove himself against me, which is a whole other story.  I’m excited for the challenge and fully expect a good, tough fight from him.  ‘However, I do expect the same outcome for him as all of the others who have challenged me before. Forty two have tried, 42 have failed. He will be No 43.’Guerrero is a six-time, four-weight world champion and proved his credentials with an impressive win over Andre Berto in November. And he is confident he can end Mayweather’s long unbeaten run.‘All of the trials and tribulations that have occurred in my life have made me a better person as well as a better fighter and the results are undeniable,’ he said.