Fix action_mailer tests

actionmailer/test/log_subscriber_test.rb

@@ -4,7 +4,11 @@
 
 class AMLogSubscriberTest < ActionMailer::TestCase
   include Rails::LogSubscriber::TestHelper
-  Rails::LogSubscriber.add(:action_mailer, ActionMailer::Railties::LogSubscriber.new)
+
+  def setup
+    super
+    Rails::LogSubscriber.add(:action_mailer, ActionMailer::Railties::LogSubscriber.new)
+  end
 
   class TestMailer < ActionMailer::Base
     def basic