AngularJS Jasmine unit test with httpBackend - rootScope variable is undefined

I have the following controller

app.controller('NavController', ['$rootScope', '$scope', 'api', function($rootScope, $scope, $location, auth, api) {
    $scope.load = function() {
        return api.get('/location').success(function(data) {
            $rootScope.locations = data;
        }).error(function(data) {
            console.log('load error');
        });
    };
}]);

And this is the unit test I have written for it

describe('Navigation Controller Test', function() {

    beforeEach(module('app'));

    var controller, scope, rootScope, httpBackend;

    beforeEach(inject(function(_$controller_, _$rootScope_, $httpBackend) {
        var $controller = _$controller_;
        rootScope = _$rootScope_;
        scope = rootScope.$new();
        httpBackend = $httpBackend;
        controller = $controller('NavController', {
            $rootScope: rootScope,
            $scope: scope,
        });

        apiRequestHandler = httpBackend.when('GET', '/api/v2/location')
            .respond({userId: 'userX'});

    }));

    afterEach(function() {
        httpBackend.verifyNoOutstandingExpectation();
        httpBackend.verifyNoOutstandingRequest();
    });

    describe('load()', function() {
        it('should have locations when successful', function() {
            httpBackend.expectGET('/api/v2/location');
            scope.load();
            expect(rootScope.locations).toEqual("{userId: 'userX'}");
            httpBackend.flush();
        });
    });
});

The current issue I'm having is that rootScope.locations is undefined even after calling the scope.load() function. I'm not too sure why this is but the closest post I seem to have found is this one which I think might be related to my problem but I'm not quite certain.

I did a console.log($rootScope.locations) in the controller when the get request is successful and it had the correct output however I'm stumped on how to get it to appear the same for this test.