Support selenium-webdriver 4

* Use public API to add argument to the selenium driver.

  While `args` is also public API it doesn't know how to handle if no
  argument is being set yet in Selenium 4.

* Fix assertions to match return on Selenium 4

Gemfile

@@ -10,7 +10,7 @@ gemspec
 gem "rake", ">= 11.1"
 
 gem "capybara", ">= 3.26"
-gem "selenium-webdriver", ">= 3.141.592"
+gem "selenium-webdriver", ">= 4.0.0.alpha7"
 
 gem "rack-cache", "~> 1.2"
 gem "sass-rails"

Gemfile.lock

@@ -193,7 +193,7 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (~> 1.5)
       xpath (~> 3.2)
-    childprocess (3.0.0)
+    childprocess (4.0.0)
     coffee-script (2.4.1)
       coffee-script-source
       execjs
@@ -455,9 +455,10 @@ GEM
       tilt
     sdoc (2.0.3)
       rdoc (>= 5.0)
-    selenium-webdriver (3.142.7)
-      childprocess (>= 0.5, < 4.0)
+    selenium-webdriver (4.0.0.alpha7)
+      childprocess (>= 0.5, < 5.0)
       rubyzip (>= 1.2.2)
+      websocket (~> 1.0)
     semantic_range (2.3.0)
     sequel (5.38.0)
     serverengine (2.0.7)
@@ -605,7 +606,7 @@ DEPENDENCIES
   rubocop-rails
   sass-rails
   sdoc (>= 2.0.3)
-  selenium-webdriver (>= 3.141.592)
+  selenium-webdriver (>= 4.0.0.alpha7)
   sequel
   sidekiq
   sneakers
@@ -625,4 +626,4 @@ DEPENDENCIES
   websocket-client-simple!
 
 BUNDLED WITH
-   2.1.4
+   2.2.3

actionpack/lib/action_dispatch/system_testing/browser.rb

@@ -71,14 +71,14 @@ module ActionDispatch
 
         def set_headless_chrome_browser_options
           configure do |capabilities|
-            capabilities.args << "--headless"
-            capabilities.args << "--disable-gpu" if Gem.win_platform?
+            capabilities.add_argument("--headless")
+            capabilities.add_argument("--disable-gpu") if Gem.win_platform?
           end
         end
 
         def set_headless_firefox_browser_options
           configure do |capabilities|
-            capabilities.args << "-headless"
+            capabilities.add_argument("-headless")
           end
         end
     end

actionpack/test/dispatch/system_testing/driver_test.rb

@@ -69,7 +69,8 @@ class DriverTest < ActiveSupport::TestCase
         "args" => ["start-maximized"],
         "mobileEmulation" => { "deviceName" => "iphone 6" },
         "prefs" => { "detach" => true }
-      }
+      },
+      "browserName" => "chrome"
     }
     assert_equal expected, browser_options[:options].as_json
   end
@@ -88,7 +89,8 @@ class DriverTest < ActiveSupport::TestCase
         "args" => ["--headless", "start-maximized"],
         "mobileEmulation" => { "deviceName" => "iphone 6" },
         "prefs" => { "detach" => true }
-      }
+      },
+      "browserName" => "chrome"
     }
     assert_equal expected, browser_options[:options].as_json
   end
@@ -105,7 +107,8 @@ class DriverTest < ActiveSupport::TestCase
       "moz:firefoxOptions" => {
         "args" => ["--host=127.0.0.1"],
         "prefs" => { "browser.startup.homepage" => "http://www.seleniumhq.com/" }
-      }
+      },
+      "browserName" => "firefox"
     }
     assert_equal expected, browser_options[:options].as_json
   end
@@ -122,7 +125,8 @@ class DriverTest < ActiveSupport::TestCase
       "moz:firefoxOptions" => {
         "args" => ["-headless", "--host=127.0.0.1"],
         "prefs" => { "browser.startup.homepage" => "http://www.seleniumhq.com/" }
-      }
+      },
+      "browserName" => "firefox"
     }
     assert_equal expected, browser_options[:options].as_json
   end