How to Use Rspec to Test That a Model Using Paperclip Is Validating The Size of an Uploaded File

How can I use Rspec to test that a model using Paperclip is validating the size of an uploaded file?

The best way I've done this is to use the built-in shoulda matchers for Paperclip. The documentation at that link is really good, but here's an overview from the docs of what you can do with it:

In spec_helper.rb, you'll need to require the matchers:

require "paperclip/matchers"

And include the module:

Spec::Runner.configure do |config|
  config.include Paperclip::Shoulda::Matchers
end

Example that validates the attachment size:

describe User do
  it { should validate_attachment_size(:avatar).
                less_than(2.megabytes) }
end

If you're interested, the source for the matchers can be found on GitHub

Unit testing paperclip uploads with Rspec (Rails)

This should work with Rails 2.X:

Image.new :photo => File.new(RAILS_ROOT + '/spec/fixtures/images/rails.png')

As of Rails 3, RAILS_ROOT is no longer used, instead you should use Rails.root.

This should work with Rails 3:

Image.new :photo => File.new(Rails.root + 'spec/fixtures/images/rails.png')

Definitely get the RSpec book, it's fantastic.

Rails: Testing file upload validation (Shrine gem) at model spec

I would recommend that you test metadata extraction and validation separately. The metadata extraction you need to test with real IOs, but for validation tests you can assign a cached file with the desired metadata which doesn't have to actually exist.

RSpec.describe ImageUploader do
  def uploaded_file(metadata = {})
    Shrine.uploaded_file(
      "id"       => "123",
      "storage"  => "cache",
      "metadata" => {"mime_type" => "image/jpeg", "size" => 100}.merge(metadata)
    )
  end

  let(:share_image) do
    FactoryGirl.build(:share_image, image: uploaded_file(metadata).to_json)
  end

  let(:metadata) { Hash.new }

  describe "validations" do
    before(:each) { share_image.valid? }

    context "when image is correct" do
      it "passes" do
        expect(share_image.errors).to be_empty
      end
    end

    context "when extension is correct but MIME types isn't" do
      let(:metadata) { Hash["filename" => "image.jpg", mime_type => "text/plain"] }

      it "fails" do
        expect(share_image.errors[:image].to_s).to include("isn't of allowed type")
      end
    end

    context "when file is larger than 10MB" do
      let(:metadata) { Hash["size" => 11 * 1024 * 1024] }

      it "fails" do
        expect(share_image.errors[:image].to_s).to include("too large")
      end
    end
  end
end

Validate a model

If you are open for adding a new gem then I would highly recommend using popular Paperclip gem which has built-in validations for file size, content type/ extension and presence.

Refer to Paperclip Github Documentation.

It would be as simple as saying

validates_attachment :image, :presence => true,
  :content_type => { :content_type => ["image/jpg", "image/jpeg", "image/gif", "image/png"] },
  :size => { :in => 0..10.kilobytes }

For a model with field named image(Paperclip attachment).

Where:

:presence Validates that a file was attached while form submission

:content_type Validates file extensions(mime-type) specified. It will also check the actual content of the uploaded file. Read my findings here.

:size Validates the uploaded file size against the given range.

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