ActionDispatch::SystemTestCase#fill_in_rich_text_area  can  locate and fill a Trix editor with the given HTML in your system tests.

The changes introduced by this pull request made ActiveRecord#respond_to?  1.5x faster and it also no longer allocates strings.

If you are using S3 with Active Storage, now you can upload large files and the services will transparently switch to streaming.

With this change, a quite expensive to_hash call is bypassed in the constructor if we are already dealing with a hash.

Rails 6 is bringing Action Mailbox and with this change, it will be possible to check which mailbox an email is routed to without processing it.