dub: standard project: how to build the unittest (the thing `dub test` runs)

[Tobias Pankrath]

Whenever I come back to some D, I seem to be stumbling over dub. 
Somehow dub and I don't align:

$ dub init dubtest && cd dubtest
$ dub test
-> creates executable `dubtest` (saying Falling back to "dub -b 
unittest".)

$ touch source/lib.d
dub test
-> creates executable dubtest-test-library

Question is: How do I build the `dubtest-test-library` without 
running the tests?

> If no explicit configuration is given, an existing "unittest" 
> configuration will be preferred for testing. If none exists, 
> the first library type configuration will be used, and if that 
> doesn't exist either, the first executable configuration is 
> chosen.

I've tried

$ dub test -b unittest -c library

but that re-creates ./dubtest not ./dubtest-test-library.