Test a phone without a screen?

[Meowster]

I recently picked up myself a Samsung Galaxy S6 in gold which lookes very nice. When I picked it up from the seller on facebook marketplace, I noticed the back glass was bulging because the battery had expanded. No big deal, got a new battery for £7.50, installed it and moved on. The main issue is that it has no AMOLED panel or digitizer. I am confident the device works, as it reports as "Fast charging" on my power bank and the phone gets hot whilst charging, and I can even feel it warming up after a while after holding down the power button. My only main concern is that there may be a fault. Look, I'm no expert on older Samsung phones but my S6 isnt vibrating, showing the blue/teal LED upon startup and the capacitive home/back buttons aren't lighting up either. Is this all happening due to the missing display?

And also, I have flashed the latest official Android 7 ROM for it and it appeared to pass according to odin. So my question is, can I somehow test this device without a screen before I make an expensive purchase of an official AMOLED for nearly £70? I do believe the phone should be at the "Welcome" screen where you select the languages and all that stuff, but can't be 100% sure