add the specs

lib/tasks/gitlab/uploads/migrate.rake

-require 'gitlab/utils/bisect_enumerable.rb'
-require_relative 'helpers.rb'
+require_relative 'helpers'
+
+include UploadTaskHelpers
 
 module UploadTask
   module Migrate
@@ -102,14 +103,14 @@ namespace :gitlab do
         uploader_class,
         model_class,
         mounted_as,
-        ObjectStorage::Store::LOCAL
+        ObjectStorage::Store::REMOTE
       )
 
       migrator.migrate(batch_size) do |results|
         UploadTask::Migrate::Reporter.new(results).report
       end
 
-      puts "\n === Migration summary ==="
+      puts "\n=== Migration summary ==="
       migrator.report
     end
   end

spec/tasks/gitlab/uploads_rake_spec.rb

@@ -24,4 +24,61 @@ describe 'gitlab:uploads rake tasks' do
       expect { run_rake_task('gitlab:uploads:check') }.to output(/File checksum \(9e697aa09fe196909813ee36103e34f721fe47a5fdc8aac0e4e4ac47b9b38282\) does not match the one in the database \(#{upload.checksum}\)/).to_stdout
     end
   end
+
+  describe 'migrate' do
+    let!(:projects) { create_list(:project, 10, :with_avatar) }
+    let(:model_class) { Project }
+    let(:uploader_class) { AvatarUploader }
+    let(:mounted_as) { :avatar }
+    let(:batch_size) { 3 }
+
+    before do
+      ENV['BATCH'] = batch_size.to_s
+      stub_uploads_object_storage(uploader_class)
+      Rake.application.rake_require 'tasks/gitlab/uploads/migrate'
+    end
+
+    def run
+      args = [uploader_class.to_s, model_class.to_s, mounted_as].compact
+      run_rake_task("gitlab:uploads:migrate", *args)
+    end
+
+    shared_examples 'outputs correctly' do |success: 0, failures: 0|
+      total = success + failures
+
+      it 'outputs the results for each batch' do
+        batch_count = [batch_size, total].min
+
+        expect { run }.to output(%r{Migrated #{batch_count}/#{batch_count} files}).to_stdout
+      end if success > 0
+
+      it 'outputs the results for the task' do
+        expect { run }.to output(%r{Migrated #{success}/#{total} files}).to_stdout
+      end if success > 0
+
+      it 'outputs upload failures' do
+        expect { run }.to output(/Error .* I am a teapot/).to_stdout
+      end if failures > 0
+    end
+
+    it_behaves_like 'outputs correctly', success: 10
+
+    it 'migrates files' do
+      run
+
+      aggregate_failures do
+        projects.each do |project|
+          expect(project.reload.avatar.upload.local?).to be_falsey
+        end
+      end
+    end
+
+    context 'migration is unsuccessful' do
+      before do
+        allow_any_instance_of(ObjectStorage::Concern).to receive(:migrate!).and_raise(CarrierWave::UploadError, "I am a teapot.")
+      end
+
+      it_behaves_like 'outputs correctly', failures: 10
+    end
+  end
 end