In recent version of Skype the Video Call button is greyed out when the contact selected is offline. Once that contact's status shows online, the button should become bright green and clickable.
The video test service that used to be run by Bill Campbell is no longer available. Unfortunately, Skype has no such test service available now and your only option is a test call with one of your contacts.
Did you read the post immediately above yours? It explains why your video call button is the way you're seeing it.