We use Capybara along with Chrome Headless for integration testing. I'd like to write a linter, that checks some metrics on the HTML structure everytime chrome navigates to another page. Then I'd raise an error when something is against our linter.
We have some tests without javascript, and monkey patching rack-test works so far:
Capybara::RackTest::Browser.class_eval do
alias_method :process_orig, :process
def process *args
response = process_orig *args
# do some linting
response
end
end
But I haven't found a way inside Capybara and/or Chrome Headless where I could intercept a response, and check the body of the page.
Is it possible to trigger a hook, when a page changes? Or is there some kind of API Chrome provides where I could get the body of every request? Or would a proxy be a feasible solution?
This isn't possible directly with Capybara, since it doesn't actually know about page transitions/requests that happen in the browser unless they are specifically user initiated with visit.
A potential way to do what you want would be using a programmable proxy like puffing-billy to handle every request to the app under test. If you use puffing-billy you'll want to look at the pass_request feature - https://github.com/oesmith/puffing-billy#in-your-tests-capybarawatir - to forward on the initial request and then do whatever you want with the response.