1 files changed, 10 insertions, 0 deletions
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index ba186bda44..fa9ed868c4 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -85,6 +85,7 @@ module ApplicationTests
     end
 
     test "mailer previews are loaded from a custom preview_path" do
+      app_dir "lib/mailer_previews"
       add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
 
       mailer "notifier", <<-RUBY
@@ -254,6 +255,7 @@ module ApplicationTests
     end
 
     test "mailer previews are reloaded from a custom preview_path" do
+      app_dir "lib/mailer_previews"
       add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
 
       app("development")
@@ -513,6 +515,13 @@ module ApplicationTests
       assert_match '<option selected value="locale=ja">ja', last_response.body
     end
 
+    test "preview does not leak I18n global setting changes" do
+      I18n.with_locale(:en) do
+        get "/rails/mailers/notifier/foo.txt?locale=ja"
+        assert_equal :en, I18n.locale
+      end
+    end
+
     test "mailer previews create correct links when loaded on a subdirectory" do
       mailer "notifier", <<-RUBY
         class Notifier < ActionMailer::Base
@@ -818,6 +827,7 @@ module ApplicationTests
       def build_app
         super
         app_file "config/routes.rb", "Rails.application.routes.draw do; end"
+        app_dir "test/mailers/previews"
       end
 
       def mailer(name, contents)