Use CSS Selectors in RSpec Request Specs

request_helpers.rb

def css(selector)
  html.css(selector).text
end

def html
  Nokogiri::HTML(response.body)
end

some_spec.rb

# How to use the above helpers.

RSpec.describe 'Test some page', type: :request do
  it 'has a <p> with "Title"' do
    get '/my-page'
    
    expect( css 'p' ).to include 'Title'
  end
end

thanks for the solution!
NB: you can include the Capybara::RSpecMatchers in your RSpec.configure block (mine is in rails_helper.rb) like this:

RSpec.configure do |config|
  config.include Capybara::RSpecMatchers, type: :request
end