Writing unit test cases for uitableview with content from json url

I am working on an iPhone app where I need to display a list of products from a url with imageview. I can do it easily but I have to write unit and ui test cases as well. I have good experience with development but haven't used test cases. I know I should have been using it since a long time back but I have to do it now. Can some one help me about how should I write test case when I need to load a tableview from a json url. I am using alamofire to download the json. This will give me a head start and I will write it for other parts by myself.

Regards
Pankaj