Need txt file in test.

spec/controllers/projects_controller_spec.rb

@@ -4,6 +4,7 @@ describe ProjectsController do
   let(:project) { create(:project) }
   let(:user)    { create(:user) }
   let(:jpg)     { fixture_file_upload(Rails.root + 'spec/fixtures/rails_sample.jpg', 'image/jpg') }
+  let(:txt)     { fixture_file_upload(Rails.root + 'spec/fixtures/doc_sample.txt', 'text/plain') }
 
   describe "POST #upload_image" do
     before do