I use paperclip in my app, but my controller tests are failing because of:
BlogsControllerTest#test_should_update_blog: Paperclip::AdapterRegistry::NoHandle
In Rails 5, I managed to work using :style in the path:
Paperclip::Attachment.default_options[:default_url] = "/images/folder/:style/missing.png"
and if, for example, this image doesn't exist:
<%= image_tag @photo.picture.url(:medium) %>
the result is
/images/folder/medium/missing.png