AngularJS - Unit test with $window object

I have a directive that look like this:

angular.directive('myDirective', ['$window', function(,$window){
    return {
        link: function(scope, element, attr, controller) {
            var w = angular.element($window);
            function showscroll(){
                var scrollTop = w.scrollTop();
                console.log("scrollTop:"+scrollTop);
                // some more code that works with $window scrollTop
            }
            function showsize(){
                var height = w.height();
                var width = w.width();
                console.log("window size:"+width+"x"+height);
                // some more codes that works with $window size
            }
            w.bind('scroll', function () {
                showscroll();
            });
            w.bind('resize', function () {
                showsize();
            });
            showscroll();
            showsize();

        }
    };
}]);

How can I mock $window object and do unit test to ensure showscroll() and showsize() working as expected?