[D1, unittest] Cannot turn on unittest version

[%u]

See subject^^
And why does the spec say that -unittest turns on asserts?

http://www.digitalmars.com/d/1.0/dmd-windows.html#switches
 -unittest
  compile in unittest code, turns on asserts, and sets the unittest version
identifier

http://www.digitalmars.com/d/1.0/unittest.html
 The version identifier unittest is predefined if the compilation is done with
unit tests enabled.

dmd -unittest
--
import std.stdio;

void main(){
  auto a = false;
  version (unittest){ // identifier or integer expected, not unittest.
D_unittest compiles, but still fails.
    writefln("a:",a);
  }
  assert(a); // assert is on, even without -unittest
}

unittest{
  auto b = true;
  writefln("b:",b);
}