How to test used / ex-demo speakers?

Folks,

I've been offered a pair of active speakers that have been used by a retailer for demo purposes.

The speakers are about two years old and they're Active.

Just wondering if there any method to test them and make sure they perform the should.

In fact, I have heard that pair and done visual observation so it seems to be ok.

Any thoughts how to test their built in amp etc, may be to turn them up and down for few times to identify wrong sound or whatsoever?!?!

Would appriciate your help

Cheers