Pass parameters in unit event testing karma

Testing an function like this:

$scope.$watch('value', function(newVal, oldVal) {
    if(newVal != oldVal)
      service.setValue(newVal);  
});

With a test like this:

it("$watch value",function(){
        spyOn(service,'setValue').andCallThrough();
        var controller=createController();
        scope.value = true;
        expect(service.setservicealue).toHaveBeenCalled();
}) 

And the spy is never triggered because of the condition. How can I trigger this watch event with the parameters in order to test if the service is called?