Extract EE only oauth routes and add tests

config/routes.rb

@@ -34,6 +34,8 @@ Rails.application.routes.draw do
     match '*all', via: [:get, :post], to: proc { [404, {}, ['']] }
   end
 
+  draw :oauth
+
   use_doorkeeper_openid_connect
 
   # Autocomplete

lib/gitlab/patch/draw_route.rb

@@ -13,11 +13,15 @@ module Gitlab
       end
 
       def draw_ce(routes_name)
-        draw_route(Rails.root.join("config/routes/#{routes_name}.rb"))
+        draw_route(route_path("config/routes/#{routes_name}.rb"))
       end
 
       def draw_ee(routes_name)
-        draw_route(Rails.root.join("ee/config/routes/#{routes_name}.rb"))
+        draw_route(route_path("ee/config/routes/#{routes_name}.rb"))
+      end
+
+      def route_path(routes_name)
+        Rails.root.join(routes_name)
       end
 
       def draw_route(path)

spec/lib/gitlab/patch/draw_route_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Gitlab::Patch::DrawRoute do
+  subject do
+    Class.new do
+      include Gitlab::Patch::DrawRoute
+
+      def route_path(route_name)
+        File.expand_path("../../../../#{route_name}", __dir__)
+      end
+    end.new
+  end
+
+  before do
+    allow(subject).to receive(:instance_eval)
+  end
+
+  it 'evaluates CE only route' do
+    subject.draw(:help)
+
+    expect(subject).to have_received(:instance_eval)
+      .with(File.read(subject.route_path('config/routes/help.rb')))
+      .once
+
+    expect(subject).to have_received(:instance_eval)
+      .once
+  end
+end