I really don’t know what counts as a good test track. All I do is listen to songs I am very familiar with.
This is usually my go-to:
I think you just need to find what works best for you. Listen to songs you are the most familiar with and notice the differences in your experience with the gear. Besides, I think you should listen to the music that you like, (not what the “best test tracks” are) because you will be listening to that music anyways on that gear.