[abalone]

You wouldn’t need to test it like that. What’s missing here is simply a test of that StorageKit API that the GUI uses. The test would be straightforward: set all the options and see if the resulting volume is created correctly. So for the hint your test would generate a value — a good test will exercise a range of values over multiple iterations — and verify the hint on the created volume.

No doubt this basic test was done on the command line API, which works correctly. It’s likely the problem here is they created a separate StorageKit API just for Disk Utility to use and got sloppy with the unit test for that. A good example of why it is a good idea to try to have GUIs and command lines use one code path whenever possible.