[FooBarWidget]

You can use AI to verify its own work. Last time I split a C++ header file into header + implementation file. I noticed some code got rewritten in a wrong manner, so I asked it to compare the new implementation file against the original header file, but to do so one method at a time. For each method, say whether the code is exactly the same and has the same behavior, ignoring superficial syntax changes and renames. Took me a few times to get the prompt right, though.