Unit testing call a function of a controller with Karma and Jasmine

This is my angular controller :-

    angular.module('authoring-controllers', []).
    controller('NavCtrl', function($scope, $location, BasketNavigationService) {
        $scope.showBasketList = BasketNavigationService.showBasketList();
    });

TEST class

describe('NavCtrl', function() {
    var scope, $location, createController;

    beforeEach(inject(function ($rootScope, $controller, _$location_) {
        $location = _$location_;
        scope = $rootScope.$new();

        createController = function() {
            return $controller('NavCtrl', {
                '$scope': scope
            });
        };
    }));

    it('should create $scope.showBasketList when calling showBasketList', 
        function() {
          expect(scope.showBasketList).toBeUndefined();
          scope.showBasketList();
          expect(scope.showBasketList).toEqual("Hello Ari");
      });
});

Getting an error when i run that test case :- scope.showBasketList() is undefined..

If i removed BasketNavigationService functionality from controller then it is working..

Please help me to solve that karma test case.