Ref: http://www.digitalmars.com/pnews/read.php?server=news.digitalmars.com&group=digitalmars.D.learn&artnum=28755

Is it possible to run unittests in libraries?
The following doesn't work:

l.d
===
module l;
import std.stdio;
int f() { return 1; } // just to make sure it's actually compiled in
unittest {
    writeln("Unittest from lib");
    assert(false);
}


t.d
===
import l;
import std.stdio;
void main() {
    writeln(f());
}


> dmd -unittest -lib l
> dmd -unittest t l.lib
> t.exe
1 // should write "Unittest from lib" and assert