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. The bitcoin network is still stable. However, look how much dissatisfaction there is from lovers of cheap transactions. There are even calls to declare the current version of bitcoin wrong and return everything as it was by the method of dividing the network.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.I am not as well informed about the vision Satoshi had for Bitcoin beyond the first years of existence. But I assume he would picture mining to become profitable eventually as his project grew through time.
Because, obviously he needed to created a good reason for the miners to work and there is no better universal incentive in this life than money and love. Unfortunately much of the love and passion for the project is long gone now profitability is more important.
It makes me kind of sad to see the Mempool in such state, to be honest.