Your ISP is going to use registered IP addresses and websites. You said yourself that you have www.test.com registered without an IP address. Therefore your ISP will not be able to find the website.
You would need to register the website name with an IP address. I would recommend that you register a website with a unique name. Many people use their last name if they want it for professional reasons.
The name doesn't mean much, it is the public IP address that is registered in DNS that is required.