QtScript evaluation question

[QPlace]

I started to learn QtScript, creating following classes:

template <typename T> class Scriptable
{
public:
   Scriptable() {}
   static void registerWithScript(const char* scriptObjName, QScriptEngine& scriptengine)
   {
    T* t = new T();
	QScriptValue obj = scriptengine.newQObject(t, QScriptEngine::ScriptOwnership);
	scriptengine.setDefaultPrototype(qMetaTypeId<T>(),obj);
 
	QScriptValue testCtor = scriptengine.newFunction(testConstructor, obj);
		scriptengine.globalObject().setProperty(scriptObjName, testCtor);
   }
private:
   static QScriptValue testConstructor(QScriptContext* /* context */,
                  	QScriptEngine *interpreter)
   {
 	return interpreter->toScriptValue(T());
   }
};
 
 
class test : public QObject, public QScriptable, public Scriptable<test>
{
	Q_OBJECT
	Q_PROPERTY(int val READ val WRITE set)
public:
	test (int i = 0) : _i(i) {	}
	test (const test& another) : _i(another._i){}
	virtual ~test ()  {}
	void set(int i) 
	{
		_i = i;
	}
	int val() 
	{	
		return _i;
	}
 
private:
	int _i;
};

template <typename T> class Scriptable
{
public:
   Scriptable() {}
   static void registerWithScript(const char* scriptObjName, QScriptEngine& scriptengine)
   {
    T* t = new T();
	QScriptValue obj = scriptengine.newQObject(t, QScriptEngine::ScriptOwnership);
	scriptengine.setDefaultPrototype(qMetaTypeId<T>(),obj);

	QScriptValue testCtor = scriptengine.newFunction(testConstructor, obj);
		scriptengine.globalObject().setProperty(scriptObjName, testCtor);
   }
private:
   static QScriptValue testConstructor(QScriptContext* /* context */,
                  	QScriptEngine *interpreter)
   {
 	return interpreter->toScriptValue(T());
   }
};


class test : public QObject, public QScriptable, public Scriptable<test>
{
	Q_OBJECT
	Q_PROPERTY(int val READ val WRITE set)
public:
	test (int i = 0) : _i(i) {	}
	test (const test& another) : _i(another._i){}
	virtual ~test ()  {}
	void set(int i) 
	{
		_i = i;
	}
	int val() 
	{	
		return _i;
	}

private:
	int _i;
};

To copy to clipboard, switch view to plain text mode 

Q_DECLARE_METATYPE(test)

Then I wrote two short scripts:
Script A:

var t = new test()
t.val = 15
t.val = t.val + 7

var t = new test()
t.val = 15
t.val = t.val + 7

To copy to clipboard, switch view to plain text mode 

and Script B

var t = new test()
t.val = 15
var m = new test()
m.val = 20
t.val + m.val

var t = new test()
t.val = 15
var m = new test()
m.val = 20
t.val + m.val

To copy to clipboard, switch view to plain text mode 

I run into following problem:
When I execute the script A – everything works fine, script returns 22 as I expect.
But when I execute script B it retuns 40, instead of expected 35. It appears as if variable “t” is replaced with “m” and therefore it returns double of whatever I assign to m.val and "t" is lost.

Below is what I do to run the script:

QString script = ui.txtRequest->toPlainText(); // script text
QScriptEngine interpreter;
test::registerWithScript("test", interpreter);
QScriptValue result = interpreter.evaluate(script);

QString script = ui.txtRequest->toPlainText(); // script text
QScriptEngine interpreter;
test::registerWithScript("test", interpreter);
QScriptValue result = interpreter.evaluate(script);

To copy to clipboard, switch view to plain text mode 

Any advice is greatly appreciated