Add DemoController tests

spec/controllers/demo_controller_spec.rb

@@ -0,0 +1,18 @@
+require 'spec_helper'
+
+describe DemoController, type: :controller do
+  describe 'GET #index' do
+
+    subject { get :index }
+
+    it { expect(subject.status).to eq 200 }
+
+    context 'when rails environnement is production' do
+      before do
+        allow(Rails).to receive(:env).and_return(ActiveSupport::StringInquirer.new("production"))
+      end
+
+      it { expect(subject.status).to eq 302 }
+    end
+  end
+end