Testing and Rspec are new to me. Currently I'm using Rspec with Shoulda and Capybara to test my application. It's all fine to test models, controllers, helpers, routing and requests. But what should I exactly test in views? Actually I want to test everything in views, including DOM, but I also don't want to overdone things.
These three things would be a good starting point
Use Capybara to go start at the root of your site, and have it click on links and whatever until it gets to the view you want tested.
Make sure what ever content is supposed to be on the page, is actually showing up on the page. So, if they 'user' went to the Product 1 page, make sure all the Product 1 content is actually there.
If different users see different content, make sure that's working. So, if Admin users see Admin-type buttons, make sure the buttons are they when the user is an Admin, and that aren't when the user isn't.
Those 3 things are a pretty good base. Even the first one is a big win. That will catch any kind of weird view syntax errors you may have accidentally introduced, as the syntax error will fail the test.