How to assert url was called from javascript using rspec and capybara - ruby-on-rails

Question

Scenario:
We use capybara integration tests to test that our frontend plumbing (javascript) is connected properly.
Sometimes all we need to validate the test is:
has content rendered properly on the page
has the js called the correct url open interaction
Problem:
Item 1 above is easy. However, with item 2 I can't seem to find an easy way to say:
Assert that url was called from js in browser.
Example:
it "should call coorect url with correct query string" do
visit widgets_path
# THIS IS WHAT I NEED TO KNOW
expect(something).to receive(:some_method).with(url: "my/test/url", params: {per_page: 2})
# In other words, I don't want the controller action to run. I don't care about the result since the controller is being tested elsewhere.
# I just need to know that the correct URL was called with the correct params.
within 'ul.pagination' do
click_on '2'
end
end
I've tried mocking the controller action, but there's no way to inspect the params. Or is there? Without inspecting the params, how can I know if the correct stuff was sent? All I know it's the correct route, which isn't enough.
If I could inspect the params then this would be solved... but otherwise?

Answer 1

If you are looking for the Rails solution, here it is! Tested with Rails 5.1.3.
1) Create a request params matcher spec/support/matchers/request_with_params.rb
RSpec::Matchers.define :request_with_params do |params|
match { |request| request.params.symbolize_keys.slice(*params.keys) == params }
end
2) Create a helper method for your acceptance tests (you can use some logics to pass symbol instead of class UsersController -> :users if needed)
def expect_request(controller, action, params = {})
expect_any_instance_of(ActionDispatch::Routing::RouteSet::Dispatcher)
.to receive(:dispatch)
.with(controller, action.to_s, request_with_params(params), anything)
end
end
3) Use it!
expect_request(UsersController, :index)
or with params
expect_request(UsersController, :show, { id: 1 })
OR
4) There is another way in using https://github.com/oesmith/puffing-billy Check this gem for intercepting requests sent by your browser. But it can be an overkill if you need to mock only certain requests to your backend app.

Answer 2

Capybara integration tests intentionally don't support that. They are end-to-end blackbox tests, shouldn't generally be mocked, and really only support checking for things visible to the user in the browser. In your example case that would mean expecting on whatever visible change is caused by the JS call to the specific URL. Something like
expect(page).to have_css('div.widget', count: 2)