Templates in external files doesn't work well

[Alex12361]

It works but when i try to move class and methods to separate files it throws errors

  #include <iostream>

using namespace std;

template<typename T>
class Test
{
    public:
        Test();
        virtual ~Test();

    protected:

    private:
        T* val;
};

template<typename T>
Test<T>::Test()
{
    //ctor
}
template<typename T>
Test<T>::~Test()
{
    //dtor
}

int main()
{
    Test<int> test;

    cout << "Hello world!" << endl;
    return 0;
}

So i tried to

Test.h <- file

#ifndef TEST_H
#define TEST_H

template<typename T>
class Test
{
    public:
        Test();
        virtual ~Test();

    protected:

    private:
        T* val;
};

#endif // TEST_H

Test.cpp <- file

#include "Test.h"
template<typename T>
Test<T>::Test()
{
    //ctor
}
template<typename T>
Test<T>::~Test()
{
    //dtor
}

then include in main it throws errors

#include <iostream>
#include <Test.h>

using namespace std;

int main()
{
    Test<int> test;

    cout << "Hello world!" << endl;
    return 0;
}

it throws
undefined reference to `Test<int>::Test()
undefined reference to `Test<int>::~Test()
undefined reference to `Test<int>::~Test()

what goes wrong?

[Thomas1965]

All templates need go to the header file.
https://stackoverflow.com/questions/5612791/c-template-and-header-files