Testing with $http.backend in Angular - angularjs

Question

I have the following controller:
(function () {
angular.module('cacApp')
.controller('mainController', function ($scope, $location, geonames) {
$scope.browseCountries =
function (path) {
$location.path(path);
};
geonames.countries()
.then(function (response) {
$scope.countries = response;
})
})
}());
and have set up the following tests for it:
describe("mainController", function () {
var _geonames, _location, _scope;
beforeEach(module('cacApp'));
beforeEach(inject(function ($controller, $injector, $httpBackend) {
_geonames = $injector.get("geonames");
_location = $injector.get("$location");
_scope = $injector.get("$rootScope").$new();
httpBackend = $httpBackend;
spyOn(_location, "path");
$controller('mainController', {
$scope: _scope,
$location: _location,
geonames: _geonames
})
}))
it("should equal a length of 250", function () {
var url = 'http://api.geonames.org/countryInfoJSON?username=steveyz';
var httpResponse = [{}];
httpBackend.expectGET(url).respond(200, httpResponse);
expect(_geonames.countries.length).toBe(250);
})
})
The "$scope.countries" response from running geonames.countries() returns an array of 250 objects, and a $scope.countries.length of 250.
I want to test to verify that the length of the response is actually 250 in my code. But when I run the test currently, I get the error "Expected 0 to be 250."
Is there a specific reason why my result is showing 0 instead of 250?