Unit testing a function returning void

[Imperatorn]

On Thursday, 3 November 2022 at 10:00:27 UTC, Bruno Pagis wrote:
> Good morning,
> I have the following class:
>
> ```
> class A {
>   int[] array;
>
>   ...
>
>   void print() {
>     writeln("array = ", this.array);
>   }
> }
> ```
>
> I would like to unit test the print function (yes, I know, not 
> very useful on the above example since print is merely a 
> duplicate of writeln...). Is there a way to use assert to test 
> the output of the print function to stdout? Something like:
> ```
> A myClass= new A;
> myClass.array = [1,2];
> assert(myClass.print() == "array = [1,2]"); // I know that 
> print does not return anything so this is wrong, but you get 
> the idea :-)
> ```
> Thanks.

Just so we understand, do you want to verify that the output is 
indeed directed to stdout and not some other stream?