How to check whether the display is working or not (Only Display)

Hello all,

My question seems to be confusing, but currently I am in the same state.

Anyways, yesterday due to heavy rainfall, water went inside my MBP from behind (Hinge exhaust vent). And my wife started it to check whether its working or not in my absence, ya sad but true, and the result? of course, it worked for some time and then when we restarted, it was starting but nothing visible on screen.

I taken it to Apple Care but as usual, they asked for my kidney and lungs, I mean 35000 (around 600 USD) for the screen cost as every thing is working when he connected it to external display.

But, he noticed some signs of short circuit over the socket, where the screen display cable connects.

Hence I just want to check, whether the socket is faulty or the display ? so if any, please suggest me the ways of checking whether the display is working or not. so that I will go for the Logic board replacement.