Programming in D page 217 - unittests for custom exceptions

[Brother Bill]

On Wednesday, 21 January 2026 at 14:44:05 UTC, Erdem wrote:
> On Wednesday, 21 January 2026 at 00:08:32 UTC, Brother Bill 
> wrote:
>> Is the mistake on my side or D's side?
>
> The function's detail should be written by you.
>
>> void average(int[] a, int[] b)
>> {
>> 	throw new UnequalLengths("Unequal lengths");
>> }
>
> How can you determine the size of arrays passed to the function 
> are not the same?
>
> ```d
> int[] average(int[] a, int[] b)
> {
>     // ...
>     int[] average;
>     if (a.length != b.length)
>         throw new UnequalLengths("Unequal lengths");
>     return average;
> }
> ```

This example is a toy.   In real code, would use your comparison.
The purpose is to throw new UnequalLengths("Unequal lengths");
And for the unit test to pass it.

My question is why isn't the unittest passing it?