GPU fans not spinning, and how to run GPU stress test

Nothing is wrong with my AMD Gigabyte GPU but I noticed that it's fans are not spinning (three fan GPU) although they do start spinning when I power on my tower. I pretty certain that this is because the GPU is in a special mode where the fans don't start spinning until the GPU reaches a certain temp.

Is there any way to make the fans run automatically when the desktop is on? Or would I not want to do that?

2nd question.
What's the best way in your opinion to run a diagnostic GPU stress test? I just want to know how for my own personal edification (There's nothing wrong with my brand new GPU)

Thanks in advance!