html rendered should update as instance changes

Author: ajjahn

lib/react/test/session.rb

@@ -31,7 +31,9 @@ def force_update!
       end
 
       def html
-        React.render_to_static_markup(element)
+        # How can we get the current ReactElement w/o violating private APIs?
+        elem = Native(native[:_reactInternalInstance][:_currentElement])
+        React.render_to_static_markup(elem)
       end
     end
   end

spec/react/test/session_spec.rb

@@ -61,6 +61,12 @@ def render
         subject.mount(Greeter, message: 'world')
         expect(subject.html).to eq('<span>Hello world</span>')
       end
+
+      it 'returns the updated static html' do
+        subject.mount(Greeter)
+        subject.update_params(message: 'moon')
+        expect(subject.html).to eq('<span>Hello moon</span>')
+      end
     end
 
     describe '#update_params' do