Is that a common practice?
No, it's not, at least based on my experience. Besides the layout, you'd also have to check security, etc, etc. To make matters worse, unit tests don't run when you edit a layout, so you wouldn't know anything is wrong until after it was too late to fix things. Also, this could be a lot of overhead in terms of maintenance if you have a lot of layouts to manage.
Will it add value?
Not likely. Admins and developers alike should be following deployment processes, preferably using Git or some mechanism to easily rollback bad deployments/track changes/etc. If you're in the habit of using source control, a simple diff can tell you if anything is amiss. It's not really so much a "test" as it is a sanity check.
That said, if you wanted to verify specific elements, you can, and you don't need Selenium to do so. Thanks to the Metadata namespace, you can now query your layouts in a unit test, which you could run as part of your deployments or periodically.
Here's some code to get you started:
@istest public class TestLayoutConfigs {
@istest static void test() {
Metadata.Metadata[] components = Metadata.operations.retrieve(Metadata.MetadataType.Layout,new String[] { 'Account-Account Layout' });
System.assertEquals(1, components.size());
for(Metadata.Metadata component: components) {
Metadata.Layout layout = (Metadata.Layout)component;
// Do something for each layout
}
}
}
See the Metadata class and its related methods in the documentation for more details.