how do you guys test if a product will sell before burning money on ads?

Back when I was doing dropshipping, honestly the worst part was testing. You find a product, make the store, run ads... and a week later you find out nobody wants it. Money gone.

So how do you do it now?

• do you test before launch or just launch and pray lol

• what's the cheapest test that actually worked for you?

I've been playing with the idea of AI "shoppers" giving feedback first, before spending on real ads. Not sure if people would trust that though. Would you?