Autoload AM test case class

actionmailer/test/abstract_unit.rb

@@ -10,7 +10,6 @@ require 'rubygems'
 require 'test/unit'
 
 require 'action_mailer'
-require 'action_mailer/test_case'
 
 # Show backtraces for deprecated behavior for quicker cleanup.
 ActiveSupport::Deprecation.debug = true

railties/lib/rails/test_help.rb

@@ -8,7 +8,6 @@ require 'rack/test'
 require 'test/unit'
 require 'active_support/core_ext/kernel/requires'
 
-require 'action_mailer/test_case' if defined?(ActionMailer)
 require 'active_model/test_case'  if defined?(ActiveModel)
 
 if defined?(ActiveRecord)