Stress testing means running the CPU and GPU hard for a proper stretch so temps, crashes and flaky behaviour show up on the bench, not during your first big game night.
It does not mean the PC will never fail. Parts still die. It does mean we were not the first people to switch it on and hope. Together with a clean Windows prep, that is the minimum we call ready.
When a listing here says stress tested, that is the bar. Ask any seller what they actually run. Vague answers are a clue.
Not sure what you need?
Pick a path, run Find my PC, or message with your games and budget. We will keep it practical.