One of my side projects is the Nomad Device Lab. It’s an Open Device Lab: a shared community pool of internet-connected devices that’s free to use for testing purposes by web and app developers. If you do a Google image search for device lab, you see a lot of walls of devices. For me, this feels a bit off.
Having all the devices on the wall is okay for testing layout and general functionality, but it misses a bit part of the testing: the user experience.
One difference is the physical experience: how you hold and interact with the device. Tapping a phone mounted on a wall is not the same as the more usual use case of using it with one hand and one thumb.
Another difference is performance: the speed of the site. Even though phones and tablets (and many other types of internet-connected devices) are getting faster, they’re still slow compared to their laptop and desktop counterparts. It’s hard to gauge just how slow when you’re looking at a wall of devices all updating.
Although I’m a big fan of apps like Ghostlab and tools like BrowserSync (which I use a lot), taking the time to sit and play with your sites manually on a range of devices really lets you feel the pain of loading and interaction times.