Do not take screenshot if driver does not support screenshot

`Capybara::RackTest::Driver` does not support taking screenshots. If call
`#save_screenshot` on `Capybara::RackTest::Driver` will raise the error.

```ruby
Error:
UsersTest#test_visiting_the_index:
Capybara::NotSupportedByDriverError: Capybara::Driver::Base#save_screenshot
```

To prevent errors, if driver does not support screenshot, do not call it.

1 files changed, 25 insertions, 0 deletions

diff --git a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
index 3b4ea96c4f..d6b501b3ac 100644
--- a/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
+++ b/actionpack/test/dispatch/system_testing/screenshot_helper_test.rb
@@ -1,5 +1,6 @@
 require "abstract_unit"
 require "action_dispatch/system_testing/test_helpers/screenshot_helper"
+require "capybara/dsl"
 
 class ScreenshotHelperTest < ActiveSupport::TestCase
   test "image path is saved in tmp directory" do
@@ -25,4 +26,28 @@ class ScreenshotHelperTest < ActiveSupport::TestCase
       end
     end
   end
+
+  test "rack_test driver does not support screenshot" do
+    begin
+      original_driver = Capybara.current_driver
+      Capybara.current_driver = :rack_test
+
+      new_test = ActionDispatch::SystemTestCase.new("x")
+      assert_not new_test.send(:supports_screenshot?)
+    ensure
+      Capybara.current_driver = original_driver
+    end
+  end
+
+  test "selenium driver supports screenshot" do
+    begin
+      original_driver = Capybara.current_driver
+      Capybara.current_driver = :selenium
+
+      new_test = ActionDispatch::SystemTestCase.new("x")
+      assert new_test.send(:supports_screenshot?)
+    ensure
+      Capybara.current_driver = original_driver
+    end
+  end
 end