How to check iPhone logic board?
Technically, all you need to hook up is the LCD/digitizer and battery and you should be able to test.

That said, I don't know how you're going to test it without actually reassembling it because the connectors are so short.  Since you have to reassemble it, do it completely because one of two things will happen:


it will work which means you don't want to disassemble it again to connect the remaining components.
it won't work in which case you must disassemble it again to return it to the seller.


Taking shortcuts in this type of work always leads to a more expensive fix than you originally hoped/planned for.