Looking at the photo, this certificate is the kind of thing that anyone could produce at home on their computer.
I am not aware of any 'test' that can prove that a signature is MJ's. Unless there is a photo of him signing it, or some other corroborative evidence eg an official letter eg from Sony to say that an item was bought at a charity auction or otherwise given/sold to the recipient, there is no proof for any signature. It all comes down to 'believing the seller.' If the seller has a good reputation to maintain, eg a reputable auction house, then you can have some (not necessarily 100%) confidence in the authenticity.
Personally I would steer clear of anything without proper 'provenance' ie some sort of genuine, provable history or believable connection to MJ. On this one, I would not believe it to be authentic on the basis of the evidence shown.
(The signature itself has some similarities with 'genuine' ones, and also some differences. I don't think it is possible to judge authenticity on the basis of the signature alone, as there are some excellent fakes on the market. The key is the 'history' of the item, and the evidence provided for that history.....eg who obtained it from Michael, how, when, where....and where has it been bought and sold since, and what evidence of that 'chain' of ownership does the seller have.)