post and pre-increment operator overloading not behaving like intrinsic types. inc:EXAMPLE (please help)

//hi maybe helpful others can look at this code and
//tell me why the class code won't behave like
//intrinsic types with post and pre increment

//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 << " <- This should be the same as this one -> " <<
test2 << endl;

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

    system("pause");
}

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