How well do you know your code?
It sounds like a strange question, but please indulge me.
Maybe you’re a manager or business analyst. If this is the case, you ‘know’ the code through a translation layer in which the developers in your organization explain what it does. Sometimes you can see what it does by interacting with it as a user or by reading incident reports.
But to really know and understand what it would do – to have a grasp on how it will behave in an arbitrary situation – you need one or more developers to give you an explanation.