Add a test for SiteUpload#cache_key (#5685)

spec/models/site_upload_spec.rb

@@ -1,5 +1,13 @@
+# frozen_string_literal: true
+
 require 'rails_helper'
 
 RSpec.describe SiteUpload, type: :model do
+  describe '#cache_key' do
+    let(:site_upload) { SiteUpload.new(var: 'var') }
 
+    it 'returns cache_key' do
+      expect(site_upload.cache_key).to eq 'site_uploads/var'
+    end
+  end
 end