paperclip where to place the missing.png default image?

Question

I use paperclip in my app, but my controller tests are failing because of:

BlogsControllerTest#test_should_update_blog:
Paperclip::AdapterRegistry::NoHandlerError: No handler found for "/images/original/missing.png"
    /Users/user/.rvm/gems/ruby-2.1.2/gems/paperclip-3.5.2/lib/paperclip/io_adapters/registry.rb:19:in `handler_for'
    /Users/user/.rvm/gems/ruby-2.1.2/gems/paperclip-3.5.2/lib/paperclip/io_adapters/registry.rb:29:in `for'
    /Users/user/.rvm/gems/ruby-2.1.2/gems/paperclip-3.5.2/lib/paperclip/attachment.rb:96:in `assign'

I'm not sure where I should place the missing.png image in my code, I tried in public/assets/original/missing.png but it doesn't seem to manage it.

Also there's something odd: I have a paperclip.rb initializer line:

Paperclip::Attachment.default_options[:default_url] = "/images/default_image.png"

but still the app is looking for the missing.png

UPDATE: ok I figured that the default_url was overridden in the model:

has_attached_file :image, styles: { big: "1200X630>", thumb: "150X150" }, default_url: "/images/:style/missing.png"

I still don't know where to place the image.

UPDATE2:

the entire paperclip initializer:

Paperclip::Attachment.default_options[:styles] = { thumb: "100x100#",  small: "200x200#",  screen: "800x600#"}
Paperclip::Attachment.default_options[:default_url] = "/images/missing.png"
Paperclip::Attachment.default_options[:path] = ":rails_root/public/assets/:class/:attachment/:id_partition/:style/:hash.:extension"
Paperclip::Attachment.default_options[:url] = "/assets/:class/:attachment/:id_partition/:style/:hash.:extension"
Paperclip::Attachment.default_options[:hash_secret] = "XXXXXXXXXXXXXXXXX"
Paperclip.registered_attachments_styles_path = "public/assets/paperclip_attachments2.yml"

UPDATE3: checking the paperclip code that actually rises the code, the exception is risen by this piece of code, which is basically testing all the adapters available, the one that looks like the closest to what I want to do is the fileAdapter which tests if the string passed is a File.

I'm quite surprised from finding this, I thing I might be getting something wrong here. If I exchange the initializer line to:

Paperclip::Attachment.default_options[:default_url] = File.new "public/images/missing.png"

then the exception is different:

BlogsControllerTest#test_should_update_blog:
NoMethodError: undefined method `gsub' for #<File:public/images/missing.png>
    /Users/user/.rvm/gems/ruby-2.1.2/gems/paperclip-3.5.2/lib/paperclip/interpolations.rb:33:in `block in interpolate'
    /Users/user/.rvm/gems/ruby-2.1.2/gems/paperclip-3.5.2/lib/paperclip/interpolations.rb:32:in `each'

UPDATE4: this is what the test looks like:

  test "should update blog" do
    put :update, id: @blog, blog: { 
      author_id: @blog.author_id, 
      body: @blog.body, 
      image: @blog.image, 
      title: @blog.title
    }
    assert_redirected_to blog_path(assigns(:blog))
  end

 test "should create blog" do
    assert_difference('Blog.count') do
      post :create, blog: { 
        author_id: @blog.author_id, 
        body: @blog.body, 
        image: @blog.image, 
        title: @blog.title }
    end

    assert_redirected_to blog_path(assigns(:blog))
  end

then:

@blog.image.class
=> Paperclip::Attachment
@blog.image.url
=> "/images/missing.png"

Answer 1

For this line of code:

Paperclip::Attachment.default_options[:default_url] = "/images/default_image.png"

Paperclip is looking for images under /public/images/default_image.png

update:

so you have defined style big and thumb. Paperclip will look for img in public/images/thumb/default_image.png or public/images/big/default_image.png depending what style will you call in <% image_tag @model.image.url(:style) %>.

update #2 (according to update #4 from author's question)

gotcha! If you want model to use :default_url don't send :image in params. remove image from params and lets see how it goes`

Answer 2

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