Do not memoize document_root_element in view tests

Memoizing will not make possible to assert the output of the view if it
is changed after the first assert_select call

Related with plataformatec/simple_form#1130 and rails/rails-dom-testing#15

2 files changed, 12 insertions, 2 deletions

diff --git a/actionview/lib/action_view/test_case.rb b/actionview/lib/action_view/test_case.rb
index 7edfc436a6..af34d2ce5a 100644
--- a/actionview/lib/action_view/test_case.rb
+++ b/actionview/lib/action_view/test_case.rb
@@ -158,8 +158,7 @@ module ActionView
 
       # Need to experiment if this priority is the best one: rendered => output_buffer
       def document_root_element
-        @html_document ||= Nokogiri::HTML::Document.parse(@rendered.blank? ? @output_buffer : @rendered)
-        @html_document.root
+        Nokogiri::HTML::Document.parse(@rendered.blank? ? @output_buffer : @rendered).root
       end
 
       def say_no_to_protect_against_forgery!
diff --git a/actionview/test/template/test_case_test.rb b/actionview/test/template/test_case_test.rb
index 4582fa13ee..5697ffa317 100644
--- a/actionview/test/template/test_case_test.rb
+++ b/actionview/test/template/test_case_test.rb
@@ -293,6 +293,17 @@ module ActionView
         assert_select 'li', :text => 'foo'
       end
     end
+
+    test "do not memoize the document_root_element in view tests" do
+      concat form_tag('/foo')
+
+      assert_select 'form'
+
+      concat content_tag(:b, 'Strong', class: 'foo')
+
+      assert_select 'form'
+      assert_select 'b.foo'
+    end
   end
 
   class RenderTemplateTest < ActionView::TestCase