A portal - see definition below taken from Webopedia is just a specific type of Web Site. You would plan and test according to the Web Site Requirements and methodology in place at you company.
Definition of Portal
Commonly referred to as simply a portal, a Web site or service that offers a broad array of resources and services, such as e-mail, forums, search engines, and on-line shopping malls. The first Web portals were online services, such as AOL, that provided access to the Web, but by now most of the traditional search engines have transformed themselves into Web portals to attract and keep a larger audience.
I have not failed. I've just found 10,000 ways that won't work" --Thomas Edison