Is it possible to run a single unittest without an external library?

[Anthony]

Hello,

I'm trying to setup a minimal testing process with unittest.
However, I would like to run the tests of a single file to keep 
things fast.
At the moment,  it runs all unittests that are imported with a 
file.
eg.
`rdmd -I... source/foo.d` will run unittests bar.d if it is 
imported into foo.d

Is there a way to run the unittests in a single file via rdmd?
I couldn't find the relevant command line flags and was hoping I 
missed something or theres some sort of trick I could use.