Though not a strict requirement of the religion, veganism has been common practice in the Jains of India for thousands of years. Some Jain monks even sweep the floor as they walk to avoid killing bugs.

Not to mention Buddhist monks in some Asian countries were effectively vegan because dairy was just not part of their diet.

Besides that, though low in numbers, veganism has been active in the West for several generations.

So veganism has been tested alot more than, for example, the relatively new practice of eating meat and dairy contaminated with antibiotics and HGH.