some companie do this way. cos they have no idea though u have shown ur paper qualification they might not have idea how u will do. so they need a time to check u. that is one reason they don't give the work Visa. else if they need they can give work visa directly. So come here. show them ur best and get the offer from them.

The process they have toled is normal. don't worry.

All the best. Have a good time