Downsides to hooks: there's part of the real interface you're not testing

[carols10cents]

In section 16.3 Provide a Scriptable Interface, you list some of the downsides to adding test hooks to your system:

It’s a security risk, for one thing—if someone discovers how to access the test hooks, they may be able to determine hidden information, overwrite data, or perform other malicious actions (or simply be curious and make a mistake). Adding a scriptable interface will require additional complexity in the program, as well as additional program length and size. The interface may be a drag on performance. Finally, time spent working on the interface means less time spent writing other features of the software, or improving its quality.

I feel like some of this gets close to, but doesn't come out and say, that you're now deliberately bypassing the way real users will interact with the system and you may miss defects that happen all the time in the real interface but never happen in the scriptable interface.

[laboon]

Made explicit in 7598cb1