Add unique_file class method to FileUpload

This encapsulates the logic for loading a fixture and assigning a new
unique name (with the same extension) into a single method.

ee/spec/graphql/mutations/design_management/upload_spec.rb

@@ -13,10 +13,6 @@ describe Mutations::DesignManagement::Upload do
     described_class.new(object: nil, context: { current_user: user }, field: nil)
   end
 
-  def unique_file(upload)
-    ::Gitlab::FileUpload.new(upload).tap { |f| f.original_filename = generate(:jpeg_file) }
-  end
-
   def run_mutation(files_to_upload = files, project_path = project.full_path, iid = issue.iid)
     mutation = described_class.new(object: nil, context: { current_user: user }, field: nil)
     mutation.resolve(project_path: project_path, iid: iid, files: files_to_upload)
@@ -53,7 +49,7 @@ describe Mutations::DesignManagement::Upload do
           ['dk.png', 'rails_sample.jpg', 'banana_sample.gif']
            .cycle
            .take(Concurrent.processor_count * 2)
-           .map { |f| unique_file(fixture_file_upload("spec/fixtures/#{f}")) }
+           .map { |f| RenameableUpload.unique_file(f) }
         end
 
         def creates_designs

ee/spec/services/design_management/save_designs_service_spec.rb

@@ -21,7 +21,6 @@ describe DesignManagement::SaveDesignsService do
 
   before do
     project.add_developer(developer)
-    # allow(::DesignManagement::NewVersionWorker).to receive(:perform_async)
   end
 
   def run_service(files_to_upload = nil)
@@ -101,10 +100,10 @@ describe DesignManagement::SaveDesignsService do
 
       it 'can run the same command in parallel' do
         blocks = Array.new(10).map do
-          wrapped_files = files.map { |f| Gitlab::FileUpload.new(f) }
-          wrapped_files.each { |f| f.original_filename = generate(:jpeg_file) }
+          unique_files = %w(rails_sample.jpg dk.png)
+                          .map { |name| RenameableUpload.unique_file(name) }
 
-          -> { run_service(wrapped_files) }
+          -> { run_service(unique_files) }
         end
 
         expect { run_parallel(blocks) }.to change(DesignManagement::Version, :count).by(10)

spec/support/file_upload.rb

-# frozen_string_literal: true
-
-class Gitlab::FileUpload < SimpleDelegator
-  attr_accessor :original_filename
-end

spec/support/renameable_upload.rb

+# frozen_string_literal: true
+
+class RenameableUpload < SimpleDelegator
+  attr_accessor :original_filename
+
+  # Get a fixture file with a new unique name, and the same extension
+  def self.unique_file(name)
+    upload = new(fixture_file_upload("spec/fixtures/#{name}"))
+    ext = File.extname(name)
+    new_name = File.basename(FactoryBot.generate(:filename), '.*')
+    upload.original_filename = new_name + ext
+
+    upload
+  end
+end