Neither. Yet. There's no proof of either of them cheating.
But, for arguments sake:
Mayweather's test failing is just a rumor
Manny refusing to take the test is a fact
. Yea I know, the finally agreed to the test but wanted a 30 day cutoff. I wonder why....
Sorry to hurt anyone's feelings. If its any consolation I wouldn't be surprised if Mayweather was cheating.