Introduce raise_on_unhandled_modal browser configuration

The problem
---

When executing a system test suite that relies on `confirm`, `prompt`,
or other browser-level modals, the default behavior to ignore modally
presented dialogs can cause false negatives.

For example, a change to the implementation might accidentally introduce
a perpetually prompting confirmation modal. While the test suite outputs
"Modal window … has been opened" warnings, the underlying test still
passes.

The proposal
---

This commit proposes a new Cuprite-level `:raise_on_unhandled_modal`
option to control whether an unhandled modal warns, or raises. When set
to `true`, then false negative test would fail, rather than pass.

Author: seanpdoyle

README.md

@@ -61,6 +61,7 @@ end
 `Cuprite`-specific options are:
 
 * options `Hash`
+  * `:raise_on_unhandled_modal` (Boolean) - When set to `false`, output a warning. When set to `true`, raise an exception
   * `:url_blacklist` (Array) - array of regexes to match against requested URLs
   * `:url_whitelist` (Array) - array of regexes to match against requested URLs
 

lib/capybara/cuprite/browser.rb

@@ -7,11 +7,15 @@ module Cuprite
     class Browser < Ferrum::Browser
       extend Forwardable
 
+      attr_accessor :raise_on_unhandled_modal
+
       delegate %i[send_keys select set hover trigger before_click switch_to_frame
                   find_modal accept_confirm dismiss_confirm accept_prompt
                   dismiss_prompt reset_modals] => :page
 
       def initialize(options = nil)
+        @raise_on_unhandled_modal = options&.delete(:raise_on_unhandled_modal)
+
         super
 
         @options.url_blacklist = prepare_wildcards(options&.dig(:url_blacklist))

lib/capybara/cuprite/driver.rb

@@ -137,6 +137,7 @@ def reset!
         @paper_size = nil
         browser.url_blacklist = @options[:url_blacklist]
         browser.url_whitelist = @options[:url_whitelist]
+        browser.raise_on_unhandled_modal = @options.fetch(:raise_on_unhandled_modal, false)
         browser.reset
         @started = false
       end

lib/capybara/cuprite/page.rb

@@ -162,10 +162,13 @@ def prepare_page
             response = @modal_response || params["defaultPrompt"]
           else
             with_text = params["message"] ? "with text `#{params['message']}` " : ""
-            warn "Modal window #{with_text}has been opened, but you didn't wrap " \
+            message = "Modal window #{with_text}has been opened, but you didn't wrap " \
                  "your code into (`accept_prompt` | `dismiss_prompt` | " \
                  "`accept_confirm` | `dismiss_confirm` | `accept_alert`), " \
                  "accepting by default"
+
+            browser.raise_on_unhandled_modal ? raise(message) : warn(message)
+
             options = { accept: true }
             response = params["defaultPrompt"]
           end

spec/features/session_spec.rb

@@ -1110,6 +1110,18 @@
         expect(@session).to have_xpath("//a[@id='open-match' and @confirmed='true']")
       end
 
+      it "configured to raise warning" do
+        @session.driver.browser.raise_on_unhandled_modal = true
+
+        @session.visit "/cuprite/with_js"
+
+        expect { @session.click_link("Open for match") }.to raise_error(
+          "Modal window with text `{T}ext \\w|th [reg.exp] (chara©+er$)?` has been opened, " \
+          "but you didn't wrap your code into (`accept_prompt` | `dismiss_prompt` | `accept_confirm` " \
+          "| `dismiss_confirm` | `accept_alert`), accepting by default"
+        )
+      end
+
       it "matches on partial strings" do
         @session.visit "/cuprite/with_js"
         expect do