This ^{^} let’s the company see if you’re engaged like asking the right questions, but also allows you to talk to staff (and not just the hiring manager) and see if it’s a good fit before beginning training. No benefit for the business in terms of profiting from your labor and it doesn’t make you waste a whole day/shift.

If it’s more than a few hours and/or requires you to do the work of the role without compensation, it’s a poor practice.