Test file showing that CarrierWave 0.6 sometimes writes in real fog repository when fog is mocked

carrier_wave_test.rb

require 'test_helper'

# This test class allows us to test CarrierWave specific behaviour, the application relies on.
class CarrierWaveTest < ActiveSupport::TestCase

  # We define an artificial ActiveRecord class using CarrierWave and fog.
  class TestUser < ActiveRecord::Base
    mount_uploader :avatar do
      storage :fog
      def store_dir
        "tmp/test_users/#{model.id}"
      end
    end
  end

  def setup
    # In setup we create the table TestUser class needs.
    ActiveRecord::Base.connection.execute("CREATE TEMPORARY TABLE test_users (id INT NOT NULL AUTO_INCREMENT, avatar VARCHAR(255), PRIMARY KEY (id))")

    # Create a mock version of AWS_S3_BUCKET, unless it already exists.
    Fog.mock!
    new_fog_connection.directories.create(:key => AWS_S3_BUCKET)  unless get_fog_directory

    # Check mock repository is empty (test is making this assumption).
    assert_equal 0, get_file_count
  end

  def teardown
    # Destroy Test User instances (to delete attached files - cleaning fog directory)
    Fog.unmock!
    TestUser.destroy_all

    # Drop TestUser table, we don't need it anymore.
    ActiveRecord::Base.connection.execute("DROP TEMPORARY TABLE test_users")
  end

  # With CarrierWave 0.6, the attached file is saved in real repository even if fog in mocked, if fog was unmock and used before.
  test "CarrierWave writes in mock repository when fog is mocked, even if fog was unmocked before" do

    # Use CarrierWave with an unmock fog
    Fog.unmock!
    original_count = get_file_count
    create_test_user
    files_in_real_repository = get_file_count
    Fog.mock!
    files_in_mock_repository = get_file_count

    # We should find one additional file in real repository, and none in mock one
    assert_equal [0, original_count + 1], [files_in_mock_repository, files_in_real_repository]

    # Use CarrierWave with mock fog
    create_test_user
    files_in_mock_repository = get_file_count
    Fog.unmock!
    files_in_real_repository = get_file_count

    # We should find one additional file in mock repository
    assert_equal [1, original_count + 1], [files_in_mock_repository, files_in_real_repository]
  end

  # Return a new fog connection.
  # In the class, we use a new fog connection for each operation to maximize isolation between each fog command.
  def new_fog_connection
    return Fog::Storage.new(
        provider:             'AWS',
        aws_access_key_id:     AWS_ACCESS_KEY_ID,
        aws_secret_access_key: AWS_SECRET_ACCESS_KEY,
        region:                AWS_S3_REGION
    )
  end

  # Return fog directory from a newly created connection.
  def get_fog_directory
    return new_fog_connection.directories.get(AWS_S3_BUCKET)
  end

  # Return file count in fog directory, using a newly created connection.
  def get_file_count
    return get_fog_directory.files.size
  end

  # Create TestUser instance, with an attached CarrierWave file.
  def create_test_user
    user = TestUser.new do |u|
      u.avatar = File.open("test/fixtures/images/portray.jpg")
    end
    assert user.save
  end
end