Change inheritance structure to match the one from Rails 5 more

In the future, ApplicationSystemTestCase should inherit from
ActionDispatch::SystemTestCase and JavaScriptApplicationSystemTestCase
could possibly be removed if the `driven_by` method works as it is
promised in Rails documentation:

http://api.rubyonrails.org/v5.2/classes/ActionDispatch/SystemTestCase.html

Consider introducing another class between
ActionDispatch::IntegrationTest and other items inheriting from it, as
the general Rails practice seems to have `ApplicationIntegrationTest`,
as we do have `ApplicationRecord` and `ApplicationController`.

test/application_system_test_case.rb

@@ -0,0 +1,42 @@
+require 'test_helper'
+
+require 'database_cleaner'
+require 'selenium/webdriver'
+
+class ApplicationSystemTestCase < ActionDispatch::IntegrationTest; end
+
+class JavaScriptApplicationSystemTestCase < ApplicationSystemTestCase
+  self.use_transactional_fixtures = false
+  DatabaseCleaner.strategy = :truncation
+
+  Capybara.register_driver(:chrome) do |_app|
+    options = ::Selenium::WebDriver::Chrome::Options.new
+
+    options.add_argument('--headless')
+    options.add_argument('--no-sandbox')
+    options.add_argument('--disable-dev-shm-usage')
+    options.add_argument('--window-size=1400,1400')
+
+    Capybara::Selenium::Driver.new(Rails.application, browser: :chrome, options: options)
+  end
+
+  Capybara.register_server(:silent_puma) do |app, port, _host|
+    require 'rack/handler/puma'
+    Rack::Handler::Puma.run(app, Port: port, Threads: '0:2', Silent: true)
+  end
+
+  def setup
+    DatabaseCleaner.start
+
+    super
+
+    Capybara.current_driver = :chrome
+    Capybara.server = :silent_puma
+  end
+
+  def teardown
+    super
+
+    DatabaseCleaner.clean
+  end
+end

test/system/registrar/sign_in_test.rb

@@ -1,6 +1,6 @@
 require 'test_helper'
 
-class RegistrarSignInTest < JavascriptIntegrationTest
+class RegistrarAreaSignInTest < JavaScriptApplicationSystemTestCase
   def setup
     super
     WebMock.allow_net_connect!

test/test_helper.rb

@@ -11,9 +11,9 @@ require 'minitest/mock'
 require 'capybara/rails'
 require 'capybara/minitest'
 require 'webmock/minitest'
-require 'selenium/webdriver'
 require 'support/rails5_assetions' # Remove once upgraded to Rails 5
-require 'database_cleaner'
+
+require 'application_system_test_case'
 
 Setting.address_processing = false
 Setting.registry_country_code = 'US'
@@ -41,39 +41,3 @@ class ActionDispatch::IntegrationTest
     Capybara.use_default_driver
   end
 end
-
-class JavascriptIntegrationTest < ActionDispatch::IntegrationTest
-  self.use_transactional_fixtures = false
-  DatabaseCleaner.strategy = :truncation
-
-  Capybara.register_driver(:chrome) do |app|
-    options = ::Selenium::WebDriver::Chrome::Options.new
-
-    options.add_argument("--headless")
-    options.add_argument("--no-sandbox")
-    options.add_argument("--disable-dev-shm-usage")
-    options.add_argument("--window-size=1400,1400")
-
-    Capybara::Selenium::Driver.new(Rails.application, browser: :chrome, options: options)
-  end
-
-  Capybara.register_server(:silent_puma) do |app, port, _host|
-    require "rack/handler/puma"
-    Rack::Handler::Puma.run(app, Port: port, Threads: "0:2", Silent: true)
-  end
-
-  def setup
-    DatabaseCleaner.start
-
-    super
-
-    Capybara.current_driver = :chrome
-    Capybara.server = :silent_puma
-  end
-
-  def teardown
-    super
-
-    DatabaseCleaner.clean
-  end
-end