Intercept capybara chrome headless visits - ruby

Question

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?

Answer 1

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.

Answer 2

I'd not tangle capybara tests with HTML linting. It may seem smart at this moment, as you get a list of URL's to check for free with each test, but:
You'd probably lint each URL few times because some tests go through it
You might get failures because HTML is not perfect, even though the feature you're testing is actually ok.
You probably have something like sitemap.xml or other sources of all available URLs. I'd use it to make a separate check, which will be simple: request the URL, lint the response. Rinse and repeat.
If still not convinced, try using page.html and do sth like
expect(page.html).to pass_linter
https://github.com/teamcapybara/capybara#debugging
You can then add it as an around hook for every type: :feature spec if you want.
EDIT: here's another workaround to have every visited path. Just parse the server log file (like this cat log/devlopment.log | grep path) to get a full list if visited paths:
method=POST path=/users/login format=html controller=SessionsController action=create
status=302 duration=256.82 view=0.00 db=52.29 location=http://0.0.0.0:3000/platform/admin/dashboard params={"utf8"=>"✓", "authenticity_token"=>"ubGnWKOq8gbUE5C/aK375QQn5DpjHarUYxHtBLglGe6Lr9Ie3O5XPq90k5gr/SZbIPoDiiasvY0mGlwhzD/MsQ==", "user"=>{"email"=>"alex-3d51048235c9d1a8#toptal.io", "password"=>"[FILTERED]", "remember_me"=>"0"}, "commit"=>"Log in"} uid=983 remote_ip=127.0.0.1 x_forwarded_for= x_request_id=
method=GET path=/admin/dashboard format=html controller=XXX action=show status=200 duration=3285.54 view=1051.32 db=2016.87 params={} uid=983 remote_ip=127.0.0.1 x_forwarded_for= x_request_id=
and use it for linting.