But does Bitcoin need any stress tests? Anyone, who has been in Bitcoin for a while, knows that Bitcoin is a very rugged technology. It's not easy to break Bitcoin. Do we need any further stress testing? I doubt it.
You can evade the synthetic test, but not the challenge of real life.As to the miners, they do receive block rewards as well as transaction fees. It's a business, if it wouldn't be profitable it would not exist. I wouldn't call it sheer enthusiasm. 
The entire first year of the Bitcoin network and even more, mining was unprofitable and worked on pure enthusiasm. Now everything has changed, but do not forget about the origins.