Use escaped character in regexp

railties/test/generators/namespaced_generators_test.rb

@@ -152,7 +152,7 @@ def test_mailer_skeleton_is_created
     assert_file "app/mailers/test_app/notifier_mailer.rb" do |mailer|
       assert_match(/module TestApp/, mailer)
       assert_match(/class NotifierMailer < ApplicationMailer/, mailer)
-      assert_no_match(/default from: "from@example.com"/, mailer)
+      assert_no_match(/default from: "from@example\.com"/, mailer)
     end
   end