add test of issue id in sending mail when issue is created by mail (#17078)

git-svn-id: http://svn.redmine.org/redmine/trunk@13195 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/unit/mail_handler_test.rb

@@ -67,6 +67,7 @@ class MailHandlerTest < ActiveSupport::TestCase
     # Email notification should be sent
     mail = ActionMailer::Base.deliveries.last
     assert_not_nil mail
+    assert mail.subject.include?("##{issue.id}")
     assert mail.subject.include?('New ticket on a given project')
   end