angular testing $window.history.back()

I'm trying to test something around $window.history.back(), but I'm not seeing the expected behavior.

Here's my service logic:

angular
    .module('navigation.service', [])
    .factory('navigationService', navigationService);

navigationService.$inject = ['$window', '$location'];

function navigationService($window, $location) {
    var service = {};

    service.back = back;

    function back() {
        $window.history.back();
    }

    return service;
}

And here's my test logic:

describe('navigation.service', function() {
    var window,
        location,
        navigationService;

    beforeEach(function() {
        module('navigation.service');

        inject(function(_navigationService_, _$window_, _$location_) {
            navigationService = _navigationService_;
            window = _$window_;
            location = _$location_;

            // defaulting to the root path '/'
            location.path('/');
        });
    });

    it('can go back', function() {            
        expect(location.path()).toEqual('/');     // '/'

        location.path('/next');            
        expect(location.path()).toEqual('/next'); // '/next'

        navigationService.back();            
        expect(location.path()).toEqual('/');     // '/next' ???
    });
});

I've made comments inline to show what's happening, but the end result is that the final location.path() isn't reflecting the triggering of $window.history.back() and instead holds the previous value. Any ideas why this is the case? I've been going at this for a while now and I'm stumped.