unittests are really part of the build, not a special run

[Kagamin via Digitalmars-d]

On Monday, 30 March 2015 at 22:20:08 UTC, Andrei Alexandrescu 
wrote:
> Where I want us to be is a place where unittests are considered 
> a part of the build; it should be trivial to set things up such 
> that unittesting is virtually indistinguishable from 
> compilation and linking.

Something of the form: `rdmd -test code.d`? Though how that will 
work is a different question.