unit testing

[sleek]

Can anyone explain to me the proper way to put a unittest { ... } block into 
my code so that the only time unit tests get compiled and run is if I'm in a 
release mode?

I thought that I could simply compile with:

dmd -release mymodule.d

However, when I run the resulting executable the unit tests are getting 
executed. I can wrap the unittest { ... } block in a debug { ... } block, 
but is this really the best way?

Thanks for the help