Use a more descriptive parameter name

spec/support/common_actions/comments.rb

@@ -6,13 +6,11 @@ module Comments
     CommentNotifier.new(comment: comment).process
   end
 
-  def reply_to(original_user, manuela = nil)
-    manuela ||= create(:user)
-
+  def reply_to(original_user, replier: create(:user))
     debate  = create(:debate)
     comment = create(:comment, commentable: debate, user: original_user)
 
-    login_as(manuela)
+    login_as(replier)
     visit debate_path(debate)
 
     click_link "Reply"

spec/system/emails_spec.rb

@@ -191,7 +191,7 @@ describe "Emails" do
     end
 
     scenario "Do not send email about own replies to own comments" do
-      reply_to(user, user)
+      reply_to(user, replier: user)
       expect { open_last_email }.to raise_error("No email has been sent!")
     end