C++ post and pre-increment operator overloading does not behave like intrinsic type operators

//C++ post and pre-increment operator overloading does not behave like intrinsic types
//Version: 1.00

#include <iostream>
using std::cout;
using std::endl;
using std::ostream;

class IntWrapper
{
  friend ostream & operator<<( ostream&, const IntWrapper& );

  public:
  IntWrapper( int val = 0 ) : i(val) {;}

  IntWrapper operator+( const IntWrapper& rhs) const
  {
    //use RVO
    return IntWrapper( this->i + rhs.i );
  }

  IntWrapper& operator++()
  {
    ++this->i;
    return *this;
  }

  IntWrapper operator++(int)
  {
    IntWrapper tmp(*this);
    this->operator++();
    return tmp;
  }

  private:
  int i;

};

ostream &operator<<( ostream &, const IntWrapper & );

int main()
{
  //interesting results of the post and pre increment operators

  IntWrapper test;
  int i = 0;

  IntWrapper test1 = test + test++;
  int test2 = i + i++;

  //test1 should be the same as test2 but they are not

  cout << test1 << " for intrinsic types test1 should be the same as test2 but is not since they are not intrinsic types " <<
  test2 << endl;

  cout << i << i++ << test << test++ << endl;

  system("pause");
}

ostream &operator<<( ostream &output, const IntWrapper &r )
{
  output << r.i;
  return output;
}

The conclusion to this experiment is that due to the unspecified behavior according to clause [5/4]
of the standard the assumption that overloading post and pre increment operators will behave in the same manner as the intrinsic type operators is incorrect and not waranted by the standard.