After making changes, check the in-game Autobar log for any errors/warnings. You can find it here: Game Menu -> Interface -> AddOns -> AutoBar -> Debug -> Warnings

Spells that are not valid will be shown here, which saves a lot of time when massive changes occur (like new expansion). It does not mean that all of the spells are available to players though so this will not catch all spells that need to be removed.

When adding new Categories, check the Nameless Categories section of the in-game AutoBar log: Game Menu -> Interface -> AddOns -> AutoBar -> Debug -> Nameless Categories

It will show you if any new Buttons or Categories are lacking localization entries.