javascript - Unit Testing a function inside a angular directive using jasmine -

i have directive in angular js. adds 'src' attribute image element shown below.

myapp.directive('imageonload', ['$q',function($q) { var dpromise; function loadimg(scope,target,url) {      var deferred = $q.defer();     dpromise = deferred.promise;      var img = new image();             // onload handler (on image, not element)              img.onload = function() {                 img.onload = null;                 //target.src = url;                                                         deferred.resolve(url);             };             img.onerror = function() {                 img.onerror = null;                 //target.src = url;                                                                           deferred.resolve(url);             };             // set source image initiate load             img.src = url;              return dpromise;    }  return {     restrict: 'a',     link: function(scope, element, attrs) {         loadimg(scope,element,attrs.url).then(function(data){                 element[0].setattribute("src",attrs.url);             scope.updateloadcount();         });      } }; 

}]);

now wanted test whether attribute src added element ?using jasmine test case.

the spec have written

it("should set url after loading image",function(){      elm = angular.element("<img id='tnl_pic_2' class='ng-scope' url='http://tnl.sf-stg.com/assetrenderer/v2/thumbnail/snapfish/idy2vvuwysbxrowyw54tnw/a/xwjojeip4rcdo5d_fxw16a/d/qhac9fjtvzxe-z2exga-lg/time/belu_cfm0vcbwk85rnr7bg2015?height=160' imageonload=''>");     elm = compile(elm)(scope);     scope.$digest();     scope.img = new image();      expect(elm.attr('src')).not.tobe('');   }); 

but spec fails , there no coverage directive, src attribute never added element

as beginner in jasmine , angular , please me out in how test functionality of directive. in adv !