making the migrate reversible

app/models/appearance.rb

@@ -12,6 +12,8 @@ class Appearance < ActiveRecord::Base
   mount_uploader :logo,         AttachmentUploader
   mount_uploader :header_logo,  AttachmentUploader
 
+  has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+
   CACHE_KEY = 'current_appearance'.freeze
 
   after_commit :flush_redis_cache

db/migrate/20180119135717_add_uploader_index_to_uploads.rb

@@ -8,8 +8,13 @@ class AddUploaderIndexToUploads < ActiveRecord::Migration
 
   disable_ddl_transaction!
 
-  def change
+  def up
     remove_concurrent_index :uploads, :path
-    add_concurrent_index :uploads, [:uploader, :path], using: :btree
+    add_concurrent_index    :uploads, [:uploader, :path], using: :btree
+  end
+
+  def down
+    remove_concurrent_index :uploads, [:uploader, :path]
+    add_concurrent_index    :uploads, :path, using: :btree
   end
 end

spec/uploaders/records_uploads_spec.rb

@@ -7,13 +7,9 @@ describe RecordsUploads do
 
       storage_options Gitlab.config.uploads
       storage :file
-
-      def model
-        FactoryBot.build_stubbed(:user)
-      end
     end
 
-    RecordsUploadsExampleUploader.new
+    RecordsUploadsExampleUploader.new(build_stubbed(:user))
   end
 
   def upload_fixture(filename)
@@ -56,7 +52,7 @@ describe RecordsUploads do
         expect(upload.path).to eq uploader.upload_path
         expect(upload.model_id).to eq uploader.model.id
         expect(upload.model_type).to eq uploader.model.class.to_s
-        expect(upload.uploader).to eq uploader.class
+        expect(upload.uploader).to eq uploader.class.to_s
       end
     end