Possible solution for export : `unittest export`?

[Andrei Alexandrescu via Digitalmars-d]

On 09/02/2015 05:07 PM, deadalnix wrote:
> On Wednesday, 2 September 2015 at 09:28:49 UTC, Dominikus Dittes Scherkl
> wrote:
>>> It is not unitestable.
>> But we have concepts like "thread local per default" and message
>> passing that should make avoiding race conditions easier. And
>> concurrent code doesn't prevent us from testing all paths of templates.
>
> I was responding to the statement that you should unittest everything.
>
> That is simply not true. For some code, this is not possible, for some
> other code, it gives poor noise to signal ratio.

What would be a good litmus test "this code needs/doesn't need 
unittesting"? -- Andrei