unsure of errors in angularjs unit testing

i am trying to unit test a controller in AngularJs and i am following the AngularJs docs as a guide. http://ift.tt/R03QJb

in the guide (in the link above) they have this code in the controller

$scope.spice = "habanero";

and this code in the test

it('should set the default value of spice', function() {
      expect($scope.spice).toBe('habanero');
    });

in the controller i am testing there is some code like this:

$scope.sessionViewModel = session;

and in my test i have written this:

it('should set the default value of sessionViewModel', function(){
            expect($scope.sessionViewModel).toBe(session);
        });

yet i am getting an error saying TypeError cannot read property 'sessionViewModel' of undefined

not really sure what i have done wrong