There are many testing frameworks out there that utilize interface screenshots for comparison and here’s a library from Facebook specifically for snapshot tests called iOS-Snapshot-Test-Case.
iOS-Snapshot-Test-Case takes a snapshot of the screen when called, compares to a reference image you supply, and if the images don’t match then the test fails.
Orta has released a plugin enhancing Xcode allowing you to quickly see your snapshots within Xcode taken with iOS-Snapshot-Test-Case, and you can see the differences betweenfailed snapshot tests.
Here’s an image showing the plugin in action from the readme:
You can find the iOS-Snapshots-Test-Case library on Github here.
You can find the Snapshots for Xcode plugin on Github here.
A nice library and plugin to aid in user interface testing.