Clean up carrierwave's files for rspec.

spec_helper.rb

RSpec.configure do |config|
  # ...

  config.after(:all) do
    if Rails.env.test? 
      FileUtils.rm_rf(Dir["#{Rails.root}/spec/support/uploads"])
    end 
  end 
end
# put logic in this file or initalizer/carrierwave.rb
if defined?(CarrierWave)
  CarrierWave::Uploader::Base.descendants.each do |klass|
    next if klass.anonymous?
    klass.class_eval do
      def cache_dir
        "#{Rails.root}/spec/support/uploads/tmp"
      end 
               
      def store_dir
        "#{Rails.root}/spec/support/uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
      end 
    end 
  end 
end

https://gist.github.com/gbpereira/c065097865a96db65973

Woohoo! Thanks @gbpereira!
This was the line that I needed before the if defined? (putting here for posterity):

Dir["#{Rails.root}/app/uploaders/*.rb"].each { |file| require file }

I'm use carrierwave (2.0.1) with rails 6.0.0 and it doesn't work for me.
My solution:
initalizer/carrierwave.rb

CarrierWave.configure do |config|
  config.asset_host = ActionController::Base.asset_host
end

if Rails.env.test?
  CarrierWave.configure do |config|
    config.root = Rails.root.join('spec/support')
    config.storage = :file
    config.enable_processing = false
  end
end