symfony : how to use the crawler to test the response of each page

I am starting to get interested in unit tests and I understood we do almost what we wanted.

How can I test a page's response (make sure it returns a 200 code) ? I get lost in all the many options. Does someone have a simple example ?

I know how to generate a list of all my pages, now I want to test each of them and make sure the response is not a 500.