Dealing with Direct Upload Attachments in Tests

I was recently building a feature for the Agency of Learning where I was working with ActiveSupport to add an attachment to a model. In my implementation, I used direct uploads to first upload the attachment to s3, then submit the form with the signed ID.

Direct uploads are totally magic. You pass a hashmap containing the attachment name as the key, and the signed_id as the value and ActiveSupport handles the attachment for you.

For example, say I have a Resume model with an attached resume:

# app/models/resume.rb
class Resume < ApplicationRecord
  belongs_to :user
  has_one_attached :resume

  validates :resume, content_type: ['application/pdf']
end

Attaching and persisting the blob to an instance of Resume is straightforward.

params = { resume: uploaded_resume_signed_id }
# let's assume I have a User in my database, and a `User` `has_many :resumes`
User.last.resumes.create!(params)

When it came time to test the service object I built, I wanted to mimic the contract that my method calls would be expecting as close as possible.

In our testing stack, we’re not leaning heavily on minitest and fixtures. Instead, we’re using FactoryBot and Rspec. This means that the fixtures approach to testing these attachments prescribed in the official Ruby on Rails guides don’t quite fit the way we write our tests.

As a result, I thought I’d try to figure out a quick/simple way to generate the signed ID for the valid Blob that the ActiveRecord model is expecting. One solution? Leveraging the ActiveStorage::Blob.create_and_upload! method.

Here’s a snippet of the spec I wrote:

# resumes_update_spec.rb
let(:user) { create(:user) }
let(:uploaded_resume_signed_id) do
  ActiveStorage::Blob.create_and_upload!(
    io: Rails.root.join('spec/fixtures/bob_resume.pdf').open,
    filename: 'bob_resume.pdf',
    content_type: 'application/pdf'
  ).signed_id
end
let(:params) do
  ActionController::Parameters.new({
    profile: {
      resume: uploaded_resume_signed_id,
    }
  }).require(:profile).permit(:resume)
end

it 'associates the resume with the user' do
  expect { Resumes::Update.new(user:, params:).call! }.to change {
    user.resumes.count
  }.by(1)
end

Hopefully this post helps save you some time if you find yourself in a similar situation in the future!