Why does this opCmp function not work

[Ruby The Roobster]

So, here we have an opCmp function for a class named shape. It 
compares the .volume of each shape:

  int opCmp(shape rhs)
{
     int exp;
     if(this.volume == rhs.volume)
         exp =  0;
     else if(this.volume > rhs.volume)
         exp =  1;
     else if(this.volume < rhs.volume)
         exp = -1;
     return exp;

}

here is how I would use it:
shape test = new shape(pos);/*Ignore the constructor argument 
it's not relevant here*/
shape test1 = new shape(pos); //same variable
writeln(test == test1);
writeln(test.opCmp(test1) == 0);

Both .volume are the same, but the output says this:

false
true

note that the documentation for comparing classes with an opCmp 
function defined is said to be this: x.opCmp(y) op 0

can anybody explain this to me?