create signals in a custom QSlider class

I'm new in Qt and I'm trying to create a custom QSlider class (it inherits from QSlider). This works perfectly but when I try to create new signals and slots, it doesn'ts work. Actually, I think it's the Q_OBJECT macro which doesn't work... Indeed, I get this message from the compiler :

erreur : 1 duplicate symbol for architecture x86_64 erreur : linker command failed with exit code 1 (use -v to see invocation)

If I remove Q_OBJECT it doesn't work either as the compilers tells me :

erreur : Error: Class declaration lacks Q_OBJECT macro.

Finally, if I make my class inherit from QWidget, all is working even the Q_OBJECT macro...

Here is my .h code :

#include <QWidget>
#include <QSlider>

class mySlider : public QSlider
{
    Q_OBJECT
public:
    explicit mySlider();

signals:
    void test();

public slots:
    void nTest();
};

Here is my .cpp code (there isn't much things, I'm only trying to make this simple code work for now) :

#include "myslider.h"

mySlider::mySlider()
{

}

void mySlider::test(){

}

void mySlider::nTest() {

}