I would like to mention that a stability test can also be done on web servers and massive multiplayer online role playing games (MMORPGs) servers. Both types of servers have to be able to handle millions of users at a time.
In both cases, everything needs to be tested, including the hard drives, CPU, RAM, and even the wires that connect the server to the internet.
A friend of mine works for a web hosting company. He says they test their servers with all of their anti-hacking and anti-virus software turned on, because that’s the way the servers will usually be operating.
Stability testing helped him find and fix a few hardware problems and one incorrect software setting before he put new servers online. That saved his company’s customers from a server crash later.