There is a bug for '-unittest'?

[FrankLike via Digitalmars-d-learn]

Hello,every one:
There is a unit test for a.d,it will be pass,do you think it's 
right?
or it's my error?
/////// the file name is a.d
  class Math
{
    /// add function
    static int add(int x, int y) { return x + y; }

    ///
    unittest
    {
       // assert(add(2, 2) == 5);
        assert(add(-2,0) == 0);
    }
}

class Sum {
  int add(int x, int y) { return x + y; }

  unittest
  {
    Sum sum = new Sum;
    //assert(sum.add(-2,0) == -2);
     assert(sum.add(-2,0) == 2);
  }
}

void main()
{
}
//// build.bat
dmd -unittest a.d
pause

-------------------------end----------------------------

Thank you.