It seems that each country conducts their own dope testing for their Olympic athletes before sending them to the Olympics. There are several drugs that can’t be in an athlete’s system prior to entering the Olympics. Sometimes, athletes must be retested to make sure that they are not using the doping drugs that are not allowed. In Switzerland, there is a building that holds the drug test results. These samples are retested by this Swiss lab in order to make sure no one is cheating.
The doping tests seem to be fair for each country because the methods of testing are relatively the same with using blood or urine samples. It would be unfair if athletes were allowed to using enhancing drugs in order to win unfairly.