[leojfc]

Doesn’t this imply the need for a new language feature? So that well-defined sections of inline code can be pulled out, initial conditions set in a testing environment, and then executed independently.

I guess this could trip up if the compiler optimisations available when considering all the code at once means that the out-of-context code actually does something different in testing...

[chimprich]

Pull out well-defined sections of inline code that can be executed independently for testing? Sure, that's breaking it down into functions.

[MereInterest]

I think there is such a feature. In most languages, these are called "functions".