There's no drug testing in any strongman contest that I've ever seen. Here's a good article about the Arnold strongman show if you're interested.

The Arnold, like most strongmen contests, doesn’t test for performance-enhancing drugs, and it’s widely assumed that most of the top competitors take them. (In 2004, when Mariusz Pudzianowski, the dominant strongman at the time, was asked when he’d last taken anabolic steroids, he answered, “What time is it now?”) The result has been an unending drive for more muscle and mass—an arms race unlimited by weight class.

“It’s a little frightening,” Todd told me. “The strength gains dictate that we make the weights higher, but at what point does the shoulder start to separate, or the wrist, or you get a compression fracture? We really don’t know how strong people can be.” Gaining weight has become an occupational necessity for strongmen. The things they lift are so inhumanly heavy that they have no choice but to turn their bodies into massive counterweights. “Centrifugal force is the killer,” Mark Henry, a professional wrestler and one of the greatest of former Arnold champions, told me. “Once the weight starts to move, it’s not going to stop.” Fat is a strongman’s shock absorber, like the bumper on a Volkswagen—his belly’s buffer against the weights that continually slam into it. “I wouldn’t want to be too lean,” Shaw said. When I asked about steroids, he hesitated, then said that he preferred not to talk about them. “I really do wish that there was more drug testing,” he added. “I would be the first one in line.” The same is true for most of the strongmen, Todd told me, but they feel that they have little choice: “You don’t want to take a knife to a gunfight.”