I've successfully tested trait inheritance in my water peas. This happens quicker the more frequently that reproduction occurs, so I set their reproductive rate very high and then constructed an environment in which, if any peas were to survive, they would have to evolve. In order to eat, they would have to pass through a small hole. Needless to say, many water peas died of starvation because they were too big to fit through the hole. But not all. It didn't take long until I noticed that the entire population of water peas was smaller than the earlier generations. That trait, being the only one that was heavily favored by the environment, ended up expressing itself the most strongly. Those that were able to eat were able to survive long enough to reproduce. Interesting!