Include test helpers when ActionDispatch::IntegrationTest is loaded

As @dhh brings up, the point of `ActionDispatch::IntegrationTest` is to
allow users to test the integration of all the pieces called by a
controller. Asserting about the emails and jobs queued is part of that
task.

This commit includes the `ActionMailer::TestHelper` and
`ActiveJob::TestHelper` modules when the ActionMailer and ActiveJob
railties are initialized respectively.

1 files changed, 4 insertions, 1 deletions

diff --git a/actionmailer/lib/action_mailer/railtie.rb b/actionmailer/lib/action_mailer/railtie.rb
index 69578471b0..bb6141b406 100644
--- a/actionmailer/lib/action_mailer/railtie.rb
+++ b/actionmailer/lib/action_mailer/railtie.rb
@@ -49,7 +49,10 @@ module ActionMailer
         options.each { |k, v| send("#{k}=", v) }
       end
 
-      ActiveSupport.on_load(:action_dispatch_integration_test) { include ActionMailer::TestCase::ClearTestDeliveries }
+      ActiveSupport.on_load(:action_dispatch_integration_test) do
+        include ActionMailer::TestHelper
+        include ActionMailer::TestCase::ClearTestDeliveries
+      end
     end
 
     initializer "action_mailer.compile_config_methods" do