Document inline image mailer preview interceptor

Explain what the interceptor is used for and how to remove it.

2 files changed, 20 insertions, 7 deletions

diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 14912326fc..38516a1c1a 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -690,7 +690,7 @@ module ApplicationTests
 
       _ = ActionMailer::Base
 
-      assert_equal [ActionMailer::Previews::InlineAttachments, ::MyPreviewMailInterceptor], ActionMailer::Base.preview_interceptors
+      assert_equal [ActionMailer::InlinePreviewInterceptor, ::MyPreviewMailInterceptor], ActionMailer::Base.preview_interceptors
     end
 
     test "registers multiple preview interceptors with ActionMailer" do
@@ -703,7 +703,20 @@ module ApplicationTests
 
       _ = ActionMailer::Base
 
-      assert_equal [ActionMailer::Previews::InlineAttachments, MyPreviewMailInterceptor, MyOtherPreviewMailInterceptor], ActionMailer::Base.preview_interceptors
+      assert_equal [ActionMailer::InlinePreviewInterceptor, MyPreviewMailInterceptor, MyOtherPreviewMailInterceptor], ActionMailer::Base.preview_interceptors
+    end
+
+    test "default preview interceptor can be removed" do
+      app_file 'config/initializers/preview_interceptors.rb', <<-RUBY
+        ActionMailer::Base.preview_interceptors.delete(ActionMailer::InlinePreviewInterceptor)
+      RUBY
+
+      require "#{app_path}/config/environment"
+      require "mail"
+
+      _ = ActionMailer::Base
+
+      assert_equal [], ActionMailer::Base.preview_interceptors
     end
 
     test "registers observers with ActionMailer" do
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index 3c9de0115f..e462d2c15e 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -487,7 +487,7 @@ module ApplicationTests
     end
 
     test "plain text mailer preview with attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
@@ -524,7 +524,7 @@ module ApplicationTests
     end
 
     test "multipart mailer preview with attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
@@ -569,7 +569,7 @@ module ApplicationTests
     end
 
     test "multipart mailer preview with inline attachment" do
-      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
+      image_file "pixel.png", "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="
 
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base
@@ -612,7 +612,7 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo?part=text/html"
       assert_equal 200, last_response.status
       assert_match %r[<p>Hello, World!</p>], last_response.body
-      assert_match %r[src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca_JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="], last_response.body
+      assert_match %r[src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEWzIioca/JlAAAACklEQVQI12NgAAAAAgAB4iG8MwAAAABJRU5ErkJgggo="], last_response.body
     end
 
     test "multipart mailer preview with attached email" do
@@ -695,7 +695,7 @@ module ApplicationTests
       end
 
       def image_file(name, contents)
-        app_file("public/images/#{name}", Base64.urlsafe_decode64(contents), 'wb')
+        app_file("public/images/#{name}", Base64.strict_decode64(contents), 'wb')
       end
   end
 end