Extracted code to EE directory

app/serializers/blob_entity.rb

@@ -14,10 +14,6 @@ class BlobEntity < Grape::Entity
   expose :url, if: -> (*) { request.respond_to?(:ref) } do |blob|
     project_blob_path(request.project, File.join(request.ref, blob.path))
   end
-
-  expose :file_lock, if: -> (*) { request.respond_to?(:ref) }, using: FileLockEntity do |blob|
-    if request.project.root_ref?(request.ref)
-      request.project.find_path_lock(blob.path, exact_match: true)
-    end
-  end
 end
+
+BlobEntity.prepend(EE::BlobEntity)

ee/app/serializers/ee/blob_entity.rb

+# frozen_string_literal: true
+
+module EE
+  module BlobEntity
+    extend ActiveSupport::Concern
+
+    prepended do
+      expose :file_lock, if: -> (*) { request.respond_to?(:ref) }, using: FileLockEntity do |blob|
+        if request.project.root_ref?(request.ref)
+          request.project.find_path_lock(blob.path, exact_match: true)
+        end
+      end
+    end
+  end
+end

ee/spec/serializers/ee/blob_entity_spec.rb

+# frozen_string_literal: true
+require 'spec_helper'
+
+describe BlobEntity do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :repository) }
+  let(:blob) { project.commit('master').diffs.diff_files.first.blob }
+  let(:request) { EntityRequest.new(project: project, ref: 'master') }
+
+  let(:entity) do
+    described_class.new(blob, request: request)
+  end
+
+  context 'as json' do
+    subject { entity.as_json }
+
+    it 'exposes needed attributes' do
+      expect(subject).to include(:file_lock)
+    end
+  end
+end