I want to use a physical iPhone to test a web site I am developing without having to deploy to a public URL.
My development machine is a MacBook Air and I have it tethered to the iPhone 5S via USB. The two are unable to pair via Bluetooth (Error: "device not compatible") which I think means I cannot use Internet Sharing to access mycomputername.local from the iPhone. The Air is running Yosemite and the web server is Node.js which serves the site locally on the Air on port 3000.
Let your macbook and your iphone connect to the same LAN, then your iphone can access your macbook by its IP directly. (remember to start node server first).