Non constant member function being called inside a constant member function

[vikuseth]

#include <iostream>

class Hello {
public:
void Test() {
std::cout << "Testing" << std::endl;
}
};

class Hi {
public:
Hi()
:hello(new Hello())
{}

~Hi()
{
delete hello;
}

void Testing() const {
hello->Test();
}

private:
Hello * hello;
};

int main(int argc, char ** argv) {
Hi hi; ;
hi.Testing();
return 0;
}
As i know a non-constant member function cant be called inside a constant member function but how the above code has been compiled successfully and giving the expected result .