Using FAKE_All for future objects does not work or is my usage wrong? [closed]

Hello,

I want to use the FAKE_ALL to fake all my objects of the same class. I modified the example from the documentation of DoInstead:

class Person
{
	public:
	     int GetAverageAge() { return 0; }
};
 
class AltPerson
{
	public:         
        int ISOLATOR_TESTABLE ReturnAnotherAge()
        {
          return 10; 
        }
};

I use FAKE_ALL to fake all future instances of Person in this way:

Person* livePerson = FAKE_ALL<Person>();
AltPerson* altPerson = new AltPerson();
WHEN_CALLED(livePerson->GetAverageAge()).DoMemberFunctionInstead(altPerson, ReturnAnotherAge);
 
Person *realPerson = new Person();
ASSERT_EQ(10, realPerson->GetAverageAge());
 
ISOLATOR_CLEANUP();

Unfortuantely the original method of Person is used which returns 0.
Am I using this in the wrong way or is something else not correct?

I use Windows 10 and google test.

Thanks a lot in advance,
Michaela