Call system test driver per-instance rather than globally

Previously the system test subclasses would call `driven_by` when the
app booted and not again when the test was initialized which resulted in
the driver from whichever class was called last to be used in tests.

In rails/rails#28144 the `driven_by` method was changed to run `use` on
setup and `reset` on teardown. While this was a viable fix this really
pointed to the problem that system test `driven_by` was a global
setting, rather than a per-class setting.

To alieviate this problem calling the driver should be done on an
instance level, rather than on the global level. I added an `initialize`
method to `SystemTestCase` which will call `use` on the superclass
driver. Running the server has been moved to `start_application` so that
it only needs to be called once on boot and no options from `driven_by`
were being passed to it.

This required a largish rewrite of the tests. Each test needs to utilize
the subclass so that it can properly test the drivers.
`ActionDispatch::SystemTestCase` shouldn't be called directly anymore.

2 files changed, 1 insertions, 6 deletions

diff --git a/actionpack/lib/action_dispatch/system_testing/driver.rb b/actionpack/lib/action_dispatch/system_testing/driver.rb
index 65e43d3584..72d132d64f 100644
--- a/actionpack/lib/action_dispatch/system_testing/driver.rb
+++ b/actionpack/lib/action_dispatch/system_testing/driver.rb
@@ -12,10 +12,6 @@ module ActionDispatch
         setup
       end
 
-      def reset
-        Capybara.current_driver = @current
-      end
-
       private
         def selenium?
           @name == :selenium
@@ -31,7 +27,6 @@ module ActionDispatch
 
         def setup
           Capybara.current_driver = @name
-          @current = Capybara.current_driver
         end
     end
   end
diff --git a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
index e37f6d02aa..6de8fb74dc 100644
--- a/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
+++ b/actionpack/lib/action_dispatch/system_testing/test_helpers/screenshot_helper.rb
@@ -57,7 +57,7 @@ module ActionDispatch
           end
 
           def supports_screenshot?
-            page.driver.public_methods(false).include?(:save_screenshot)
+            Capybara.current_driver != :rack_test
           end
       end
     end