Add save_and_open_page helper to IntegrationTest

`save_and_open_page` is a capybara helper that lets developers
inspect the status of the page at any given point in their
test. This is helpful when trying to keep a short feedback loop while
working on a test.

This change adds a similar helper with matching signature to
integration tests.

Gemfile

@@ -196,3 +196,4 @@ gem "wdm", ">= 0.1.0", platforms: [:windows]
 if RUBY_VERSION < "3.2"
   gem "error_highlight", ">= 0.4.0", platforms: [:ruby]
 end
+gem "launchy"

Gemfile.lock

@@ -305,6 +305,8 @@ GEM
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
     language_server-protocol (3.17.0.3)
+    launchy (2.5.2)
+      addressable (~> 2.8)
     libxml-ruby (5.0.3)
     listen (3.8.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
@@ -613,6 +615,7 @@ DEPENDENCIES
   jbuilder
   jsbundling-rails
   json (>= 2.0.0, != 2.7.0)
+  launchy
   libxml-ruby
   listen (~> 3.3)
   mdl (!= 0.13.0)

actionpack/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Add `save_and_open_page` helper to IntegrationTest
+    `save_and_open_page` is a helpful helper to keep a short feedback loop when working on system tests.
+    A similar helper with matching signature has been added to integration tests.
+
+    *Joé Dupuis*
+
 *   Fix a regression in 7.1.3 passing a `to:` option without a controller when the controller is already defined by a scope.
 
     ```ruby

actionpack/lib/action_dispatch/testing/integration.rb

@@ -8,6 +8,7 @@
 require "active_support/test_case"
 
 require "action_dispatch/testing/request_encoder"
+require "action_dispatch/testing/test_helpers/page_dump_helper"
 
 module ActionDispatch
   module Integration # :nodoc:
@@ -651,6 +652,7 @@ module Behavior
 
       include Integration::Runner
       include ActionController::TemplateAssertions
+      include TestHelpers::PageDumpHelper
 
       included do
         include ActionDispatch::Routing::UrlFor

actionpack/lib/action_dispatch/testing/test_helpers/page_dump_helper.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  module TestHelpers
+    module PageDumpHelper
+      class InvalidResponse < StandardError; end
+
+      # Saves the content of response body to a file and tries to open it in your browser.
+      # Launchy must be present in your Gemfile for the page to open automatically.
+      def save_and_open_page(path = html_dump_defaul_path)
+        save_page(path).tap { |s_path| open_file(s_path) }
+      end
+
+      private
+        def save_page(path = html_dump_defaul_path)
+          raise InvalidResponse.new("Response is a redirection!") if response.redirection?
+          path = Pathname.new(path)
+          path.dirname.mkpath
+          File.write(path, response.body)
+          path
+        end
+
+        def open_file(path)
+          require "launchy"
+          Launchy.open(path)
+        rescue LoadError
+          warn "File saved to #{path}.\nPlease install the launchy gem to open the file automatically."
+        end
+
+        def html_dump_defaul_path
+          Rails.root.join("tmp/html_dump", "#{method_name}_#{DateTime.current.to_i}.html").to_s
+        end
+    end
+  end
+end

actionpack/test/controller/integration_test.rb

@@ -3,6 +3,7 @@
 require "abstract_unit"
 require "controller/fake_controllers"
 require "rails/engine"
+require "launchy"
 
 class SessionTest < ActiveSupport::TestCase
   StubApp = lambda { |env|
@@ -1307,3 +1308,87 @@ def test_fixture_file_upload
     assert_equal "45142", @response.body
   end
 end
+
+class PageDumpIntegrationTest < ActionDispatch::IntegrationTest
+  class FooController < ActionController::Base
+    def index
+      render plain: "Hello world"
+    end
+
+    def redirect
+      redirect_to action: :index
+    end
+  end
+
+  def with_root(&block)
+    Rails.stub(:root, Pathname.getwd.join("test"), &block)
+  end
+
+  def setup
+    with_root do
+      remove_dumps
+    end
+  end
+
+  def teardown
+    with_root do
+      remove_dumps
+    end
+  end
+
+  def self.routes
+    @routes ||= ActionDispatch::Routing::RouteSet.new
+  end
+
+  def self.call(env)
+    routes.call(env)
+  end
+
+  def app
+    self.class
+  end
+
+  def dump_path
+    Pathname.new(Dir["#{Rails.root}/tmp/html_dump/#{method_name}*"].sole)
+  end
+
+  def remove_dumps
+    Dir["#{Rails.root}/tmp/html_dump/#{method_name}*"].each(&File.method(:delete))
+  end
+
+  routes.draw do
+    get "/" => "page_dump_integration_test/foo#index"
+    get "/redirect" => "page_dump_integration_test/foo#redirect"
+  end
+
+  test "save_and_open_page saves a copy of the page and call to Launchy" do
+    launchy_called = false
+    get "/"
+    with_root do
+      Launchy.stub(:open, ->(path) { launchy_called = (path == dump_path) }) do
+        save_and_open_page
+      end
+      assert launchy_called
+      assert_equal File.read(dump_path), response.body
+    end
+  end
+
+  test "prints a warning to install launchy if it can't be loaded" do
+    get "/"
+    with_root do
+      Launchy.stub(:open, ->(path) { raise LoadError.new }) do
+      self.stub(:warn, ->(warning) { warning.include?("Please install the launchy gem to open the file automatically.") }) do
+      save_and_open_page
+    end
+    end
+      assert_equal File.read(dump_path), response.body
+    end
+  end
+
+  test "raises when called after a redirect" do
+    with_root do
+      get "/redirect"
+      assert_raise(InvalidResponse) { save_and_open_page }
+    end
+  end
+end