If you are looking for deelay ruby gem, you can find it here.
Inline delay proxy for http resources Slow loading resources (images, scripts, etc) can break your code. Test it simulating unexpected network conditions applied to specific resource.
$ npm install -g deelay
$ deelay
Starting delay on port 4567
$ docker build -t deelay .
$ docker run -p 4567:4567 deelay
Starting delay on port 4567
curl localhost:4567/1000/http://mysite.com/image.gif
node test/indexTest.js