This is awesome you contributed to so popular open source project, but it is a good and recommended practice to provide a basic test of the functionality you have fixed. I mean a test that was failing and your fix made it pass. In that and only that way you can ensure that future changes to this project (Devise) will not break your fix. :)
Absolutely correct on that. Normally I would write a test for it, but this is not core functionality to Devise and tests for little tiny things like this don't really add much other than slowing down your test suite. There are still tests that make sure the generators still run correctly so it still works. If the functionality ever got reverted back to the original on accident, it wouldn't be a big deal. You could certainly add a test, but I'd argue how much value you actually get out of it in this case.
Beautiful Chris! The `presence` method trick was really nice too. Thanks for this amazing contribution.
While watching, I was wondering what the point of calling `presence` was, when you can just use the variable name alone for that trick. It turns out `presence` also returns nil for an empty string, which makes sense in this case.