add test for X-Forwarded-Host header

spec/swagger_v2/x_forwarded_host.rb

@@ -0,0 +1,30 @@
+require 'spec_helper'
+
+describe 'respect X-Forwarded-Host over Host header' do
+  include_context "the api entities"
+
+  before :all do
+    module TheApi
+      class EmptyApi < Grape::API
+        format :json
+
+        add_swagger_documentation
+      end
+    end
+  end
+
+  def app
+    TheApi::EmptyApi
+  end
+
+  subject do
+    header 'Host', 'dummy.example.com'
+    header 'X-Forwarded-Host', 'real.example.com'
+    get '/swagger_doc'
+    JSON.parse(last_response.body)
+  end
+
+  specify do
+    expect(subject['host']).to eq 'real.example.com'
+  end
+end